Imported QtWebKit TP3 (git b57bc6801f1876c3220d5a4bfea33d620d477443)

Change-Id: I3b1d8a2808782c9f34d50240000e20cb38d3680f
Reviewed-by: Konstantin Tokarev <annulen@yandex.ru>

1 files changed, 960 insertions, 2416 deletions

diff --git a/Source/WebCore/rendering/RenderBlockLineLayout.cpp b/Source/WebCore/rendering/RenderBlockLineLayout.cpp
index c6f283a73..451de09c9 100644
--- a/Source/WebCore/rendering/RenderBlockLineLayout.cpp
+++ b/Source/WebCore/rendering/RenderBlockLineLayout.cpp
@@ -3,6 +3,7 @@
  * Copyright (C) 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All right reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2013 ChangSeok Oh <shivamidow@gmail.com>
+ * Copyright (C) 2013 Adobe Systems Inc. All right reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ -23,383 +24,45 @@
 
 #include "config.h"
 
+#include "AXObjectCache.h"
 #include "BidiResolver.h"
-#include "Hyphenation.h"
+#include "BreakingContext.h"
+#include "FloatingObjects.h"
+#include "InlineElementBox.h"
 #include "InlineIterator.h"
 #include "InlineTextBox.h"
+#include "InlineTextBoxStyle.h"
+#include "LineLayoutState.h"
 #include "Logging.h"
-#include "RenderArena.h"
-#include "RenderCombineText.h"
-#include "RenderCounter.h"
+#include "RenderBlockFlow.h"
 #include "RenderFlowThread.h"
-#include "RenderInline.h"
-#include "RenderLayer.h"
-#include "RenderListMarker.h"
+#include "RenderLineBreak.h"
 #include "RenderRegion.h"
-#include "RenderRubyRun.h"
+#include "RenderRubyBase.h"
+#include "RenderRubyText.h"
 #include "RenderView.h"
+#include "SVGRootInlineBox.h"
 #include "Settings.h"
+#include "SimpleLineLayoutFunctions.h"
 #include "TrailingFloatsRootInlineBox.h"
 #include "VerticalPositionCache.h"
-#include "break_lines.h"
 #include <wtf/RefCountedLeakCounter.h>
 #include <wtf/StdLibExtras.h>
-#include <wtf/Vector.h>
-#include <wtf/unicode/CharacterNames.h>
-
-#if ENABLE(CSS_SHAPES)
-#include "ShapeInsideInfo.h"
-#endif
-
-#if ENABLE(SVG)
-#include "RenderSVGInlineText.h"
-#include "SVGRootInlineBox.h"
-#endif
-
-using namespace std;
-using namespace WTF;
-using namespace Unicode;
 
 namespace WebCore {
 
-// We don't let our line box tree for a single line get any deeper than this.
-const unsigned cMaxLineDepth = 200;
-
-static LayoutUnit logicalHeightForLine(const RenderBlock* block, bool isFirstLine, LayoutUnit replacedHeight = 0)
-{
-    if (!block->document()->inNoQuirksMode() && replacedHeight)
-        return replacedHeight;
-
-    if (!(block->style(isFirstLine)->lineBoxContain() & LineBoxContainBlock))
-        return 0;
-
-    return max<LayoutUnit>(replacedHeight, block->lineHeight(isFirstLine, block->isHorizontalWritingMode() ? HorizontalLine : VerticalLine, PositionOfInteriorLineBoxes));
-}
-
-#if ENABLE(CSS_SHAPES)
-ShapeInsideInfo* RenderBlock::layoutShapeInsideInfo() const
-{
-    ShapeInsideInfo* shapeInsideInfo = view()->layoutState()->shapeInsideInfo();
-
-    if (!shapeInsideInfo && flowThreadContainingBlock() && allowsShapeInsideInfoSharing()) {
-        // regionAtBlockOffset returns regions like an array first={0,N-1}, second={N,M-1}, ...
-        LayoutUnit offset = logicalHeight() + logicalHeightForLine(this, false) - LayoutUnit(1);
-        RenderRegion* region = regionAtBlockOffset(offset);
-        if (region)
-            shapeInsideInfo = region->shapeInsideInfo();
-    }
-
-    return shapeInsideInfo;
-}
-#endif
-
-enum IndentTextOrNot { DoNotIndentText, IndentText };
-
-class LineWidth {
-public:
-    LineWidth(RenderBlock* block, bool isFirstLine, IndentTextOrNot shouldIndentText)
-        : m_block(block)
-        , m_uncommittedWidth(0)
-        , m_committedWidth(0)
-        , m_overhangWidth(0)
-        , m_trailingWhitespaceWidth(0)
-        , m_trailingCollapsedWhitespaceWidth(0)
-        , m_left(0)
-        , m_right(0)
-        , m_availableWidth(0)
-#if ENABLE(CSS_SHAPES)
-        , m_segment(0)
-#endif
-        , m_isFirstLine(isFirstLine)
-        , m_shouldIndentText(shouldIndentText)
-    {
-        ASSERT(block);
-#if ENABLE(CSS_SHAPES)
-        if (ShapeInsideInfo* shapeInsideInfo = m_block->layoutShapeInsideInfo())
-            m_segment = shapeInsideInfo->currentSegment();
-#endif
-        updateAvailableWidth();
-    }
-    bool fitsOnLine(bool ignoringTrailingSpace = false)
-    {
-        return ignoringTrailingSpace ? fitsOnLineExcludingTrailingCollapsedWhitespace() : fitsOnLineIncludingExtraWidth(0);
-    }
-    bool fitsOnLineIncludingExtraWidth(float extra) const { return currentWidth() + extra <= m_availableWidth; }
-    bool fitsOnLineExcludingTrailingWhitespace(float extra) const { return currentWidth() - m_trailingWhitespaceWidth + extra <= m_availableWidth; }
-
-    float currentWidth() const { return m_committedWidth + m_uncommittedWidth; }
-    // FIXME: We should eventually replace these three functions by ones that work on a higher abstraction.
-    float uncommittedWidth() const { return m_uncommittedWidth; }
-    float committedWidth() const { return m_committedWidth; }
-    float availableWidth() const { return m_availableWidth; }
-
-    void updateAvailableWidth(LayoutUnit minimumHeight = 0);
-    void shrinkAvailableWidthForNewFloatIfNeeded(RenderBlock::FloatingObject*);
-    void addUncommittedWidth(float delta) { m_uncommittedWidth += delta; }
-    void commit()
-    {
-        m_committedWidth += m_uncommittedWidth;
-        m_uncommittedWidth = 0;
-    }
-    void applyOverhang(RenderRubyRun*, RenderObject* startRenderer, RenderObject* endRenderer);
-    void fitBelowFloats();
-    void setTrailingWhitespaceWidth(float collapsedWhitespace, float borderPaddingMargin = 0) { m_trailingCollapsedWhitespaceWidth = collapsedWhitespace; m_trailingWhitespaceWidth =  collapsedWhitespace + borderPaddingMargin; }
-
-    bool shouldIndentText() const { return m_shouldIndentText == IndentText; }
-
-private:
-    void computeAvailableWidthFromLeftAndRight()
-    {
-        m_availableWidth = max(0.0f, m_right - m_left) + m_overhangWidth;
-    }
-    bool fitsOnLineExcludingTrailingCollapsedWhitespace() const { return currentWidth() - m_trailingCollapsedWhitespaceWidth <= m_availableWidth; }
-
-private:
-    RenderBlock* m_block;
-    float m_uncommittedWidth;
-    float m_committedWidth;
-    float m_overhangWidth; // The amount by which |m_availableWidth| has been inflated to account for possible contraction due to ruby overhang.
-    float m_trailingWhitespaceWidth;
-    float m_trailingCollapsedWhitespaceWidth;
-    float m_left;
-    float m_right;
-    float m_availableWidth;
-#if ENABLE(CSS_SHAPES)
-    const LineSegment* m_segment;
-#endif
-    bool m_isFirstLine;
-    IndentTextOrNot m_shouldIndentText;
-};
-
-inline void LineWidth::updateAvailableWidth(LayoutUnit replacedHeight)
-{
-    LayoutUnit height = m_block->logicalHeight();
-    LayoutUnit logicalHeight = logicalHeightForLine(m_block, m_isFirstLine, replacedHeight);
-    m_left = m_block->logicalLeftOffsetForLine(height, shouldIndentText(), logicalHeight);
-    m_right = m_block->logicalRightOffsetForLine(height, shouldIndentText(), logicalHeight);
-
-#if ENABLE(CSS_SHAPES)
-    if (m_segment) {
-        m_left = max<float>(m_segment->logicalLeft, m_left);
-        m_right = min<float>(m_segment->logicalRight, m_right);
-    }
-#endif
-
-    computeAvailableWidthFromLeftAndRight();
-}
-
-inline void LineWidth::shrinkAvailableWidthForNewFloatIfNeeded(RenderBlock::FloatingObject* newFloat)
-{
-    LayoutUnit height = m_block->logicalHeight();
-    if (height < m_block->logicalTopForFloat(newFloat) || height >= m_block->logicalBottomForFloat(newFloat))
-        return;
-
-#if ENABLE(CSS_SHAPES)
-    // When floats with shape outside are stacked, the floats are positioned based on the margin box of the float,
-    // not the shape's contour. Since we computed the width based on the shape contour when we added the float,
-    // when we add a subsequent float on the same line, we need to undo the shape delta in order to position
-    // based on the margin box. In order to do this, we need to walk back through the floating object list to find
-    // the first previous float that is on the same side as our newFloat.
-    ShapeOutsideInfo* previousShapeOutsideInfo = 0;
-    const RenderBlock::FloatingObjectSet& floatingObjectSet = m_block->m_floatingObjects->set();
-    RenderBlock::FloatingObjectSetIterator it = floatingObjectSet.end();
-    RenderBlock::FloatingObjectSetIterator begin = floatingObjectSet.begin();
-    for (--it; it != begin; --it) {
-        RenderBlock::FloatingObject* previousFloat = *it;
-        if (previousFloat != newFloat && previousFloat->type() == newFloat->type()) {
-            previousShapeOutsideInfo = previousFloat->renderer()->shapeOutsideInfo();
-            if (previousShapeOutsideInfo) {
-                previousShapeOutsideInfo->computeSegmentsForContainingBlockLine(m_block->logicalHeight(), m_block->logicalTopForFloat(previousFloat), logicalHeightForLine(m_block, m_isFirstLine));
-            }
-            break;
-        }
-    }
-
-    ShapeOutsideInfo* shapeOutsideInfo = newFloat->renderer()->shapeOutsideInfo();
-    if (shapeOutsideInfo) {
-        shapeOutsideInfo->computeSegmentsForContainingBlockLine(m_block->logicalHeight(), m_block->logicalTopForFloat(newFloat), logicalHeightForLine(m_block, m_isFirstLine));
-    }
-#endif
-
-    if (newFloat->type() == RenderBlock::FloatingObject::FloatLeft) {
-        float newLeft = m_block->logicalRightForFloat(newFloat);
-#if ENABLE(CSS_SHAPES)
-        if (previousShapeOutsideInfo)
-            newLeft -= previousShapeOutsideInfo->rightSegmentMarginBoxDelta();
-        if (shapeOutsideInfo)
-            newLeft += shapeOutsideInfo->rightSegmentMarginBoxDelta();
-#endif
-
-        if (shouldIndentText() && m_block->style()->isLeftToRightDirection())
-            newLeft += floorToInt(m_block->textIndentOffset());
-        m_left = max<float>(m_left, newLeft);
-    } else {
-        float newRight = m_block->logicalLeftForFloat(newFloat);
-#if ENABLE(CSS_SHAPES)
-        if (previousShapeOutsideInfo)
-            newRight -= previousShapeOutsideInfo->leftSegmentMarginBoxDelta();
-        if (shapeOutsideInfo)
-            newRight += shapeOutsideInfo->leftSegmentMarginBoxDelta();
-#endif
-
-        if (shouldIndentText() && !m_block->style()->isLeftToRightDirection())
-            newRight -= floorToInt(m_block->textIndentOffset());
-        m_right = min<float>(m_right, newRight);
-    }
-
-    computeAvailableWidthFromLeftAndRight();
-}
-
-void LineWidth::applyOverhang(RenderRubyRun* rubyRun, RenderObject* startRenderer, RenderObject* endRenderer)
-{
-    int startOverhang;
-    int endOverhang;
-    rubyRun->getOverhang(m_isFirstLine, startRenderer, endRenderer, startOverhang, endOverhang);
-
-    startOverhang = min<int>(startOverhang, m_committedWidth);
-    m_availableWidth += startOverhang;
-
-    endOverhang = max(min<int>(endOverhang, m_availableWidth - currentWidth()), 0);
-    m_availableWidth += endOverhang;
-    m_overhangWidth += startOverhang + endOverhang;
-}
-
-void LineWidth::fitBelowFloats()
-{
-    ASSERT(!m_committedWidth);
-    ASSERT(!fitsOnLine());
-
-    LayoutUnit floatLogicalBottom;
-    LayoutUnit lastFloatLogicalBottom = m_block->logicalHeight();
-    float newLineWidth = m_availableWidth;
-    float newLineLeft = m_left;
-    float newLineRight = m_right;
-    while (true) {
-        floatLogicalBottom = m_block->nextFloatLogicalBottomBelow(lastFloatLogicalBottom);
-        if (floatLogicalBottom <= lastFloatLogicalBottom)
-            break;
-
-        newLineLeft = m_block->logicalLeftOffsetForLine(floatLogicalBottom, shouldIndentText());
-        newLineRight = m_block->logicalRightOffsetForLine(floatLogicalBottom, shouldIndentText());
-        newLineWidth = max(0.0f, newLineRight - newLineLeft);
-        lastFloatLogicalBottom = floatLogicalBottom;
-        if (newLineWidth >= m_uncommittedWidth)
-            break;
-    }
-
-    if (newLineWidth > m_availableWidth) {
-        m_block->setLogicalHeight(lastFloatLogicalBottom);
-        m_availableWidth = newLineWidth + m_overhangWidth;
-        m_left = newLineLeft;
-        m_right = newLineRight;
-    }
-}
-
-class LineInfo {
-public:
-    LineInfo()
-        : m_isFirstLine(true)
-        , m_isLastLine(false)
-        , m_isEmpty(true)
-        , m_previousLineBrokeCleanly(true)
-        , m_floatPaginationStrut(0)
-        , m_runsFromLeadingWhitespace(0)
-    { }
-
-    bool isFirstLine() const { return m_isFirstLine; }
-    bool isLastLine() const { return m_isLastLine; }
-    bool isEmpty() const { return m_isEmpty; }
-    bool previousLineBrokeCleanly() const { return m_previousLineBrokeCleanly; }
-    LayoutUnit floatPaginationStrut() const { return m_floatPaginationStrut; }
-    unsigned runsFromLeadingWhitespace() const { return m_runsFromLeadingWhitespace; }
-    void resetRunsFromLeadingWhitespace() { m_runsFromLeadingWhitespace = 0; }
-    void incrementRunsFromLeadingWhitespace() { m_runsFromLeadingWhitespace++; }
-
-    void setFirstLine(bool firstLine) { m_isFirstLine = firstLine; }
-    void setLastLine(bool lastLine) { m_isLastLine = lastLine; }
-    void setEmpty(bool empty, RenderBlock* block = 0, LineWidth* lineWidth = 0)
-    {
-        if (m_isEmpty == empty)
-            return;
-        m_isEmpty = empty;
-        if (!empty && block && floatPaginationStrut()) {
-            block->setLogicalHeight(block->logicalHeight() + floatPaginationStrut());
-            setFloatPaginationStrut(0);
-            lineWidth->updateAvailableWidth();
-        }
-    }
-
-    void setPreviousLineBrokeCleanly(bool previousLineBrokeCleanly) { m_previousLineBrokeCleanly = previousLineBrokeCleanly; }
-    void setFloatPaginationStrut(LayoutUnit strut) { m_floatPaginationStrut = strut; }
-
-private:
-    bool m_isFirstLine;
-    bool m_isLastLine;
-    bool m_isEmpty;
-    bool m_previousLineBrokeCleanly;
-    LayoutUnit m_floatPaginationStrut;
-    unsigned m_runsFromLeadingWhitespace;
-};
-
-static inline LayoutUnit borderPaddingMarginStart(RenderInline* child)
-{
-    return child->marginStart() + child->paddingStart() + child->borderStart();
-}
-
-static inline LayoutUnit borderPaddingMarginEnd(RenderInline* child)
-{
-    return child->marginEnd() + child->paddingEnd() + child->borderEnd();
-}
-
-static inline bool shouldAddBorderPaddingMargin(RenderObject* child)
-{
-    // When deciding whether we're at the edge of an inline, adjacent collapsed whitespace is the same as no sibling at all.
-    return !child || (child->isText() && !toRenderText(child)->textLength());
-}
-
-static RenderObject* previousInFlowSibling(RenderObject* child)
-{
-    child = child->previousSibling();
-    while (child && child->isOutOfFlowPositioned())
-        child = child->previousSibling();
-    return child;
-}
-
-static LayoutUnit inlineLogicalWidth(RenderObject* child, bool checkStartEdge = true, bool checkEndEdge = true)
-{
-    unsigned lineDepth = 1;
-    LayoutUnit extraWidth = 0;
-    RenderObject* parent = child->parent();
-    while (parent->isRenderInline() && lineDepth++ < cMaxLineDepth) {
-        RenderInline* parentAsRenderInline = toRenderInline(parent);
-        if (!isEmptyInline(parentAsRenderInline)) {
-            checkStartEdge = checkStartEdge && shouldAddBorderPaddingMargin(previousInFlowSibling(child));
-            if (checkStartEdge)
-                extraWidth += borderPaddingMarginStart(parentAsRenderInline);
-            checkEndEdge = checkEndEdge && shouldAddBorderPaddingMargin(child->nextSibling());
-            if (checkEndEdge)
-                extraWidth += borderPaddingMarginEnd(parentAsRenderInline);
-            if (!checkStartEdge && !checkEndEdge)
-                return extraWidth;
-        }
-        child = parent;
-        parent = child->parent();
-    }
-    return extraWidth;
-}
-
 static void determineDirectionality(TextDirection& dir, InlineIterator iter)
 {
     while (!iter.atEnd()) {
         if (iter.atParagraphSeparator())
             return;
         if (UChar current = iter.current()) {
-            Direction charDirection = direction(current);
-            if (charDirection == LeftToRight) {
+            UCharDirection charDirection = u_charDirection(current);
+            if (charDirection == U_LEFT_TO_RIGHT) {
                 dir = LTR;
                 return;
             }
-            if (charDirection == RightToLeft || charDirection == RightToLeftArabic) {
+            if (charDirection == U_RIGHT_TO_LEFT || charDirection == U_RIGHT_TO_LEFT_ARABIC) {
                 dir = RTL;
                 return;
             }
@@ -408,149 +71,107 @@ static void determineDirectionality(TextDirection& dir, InlineIterator iter)
     }
 }
 
-static void checkMidpoints(LineMidpointState& lineMidpointState, InlineIterator& lBreak)
+inline BidiRun* createRun(int start, int end, RenderObject& obj, InlineBidiResolver& resolver)
 {
-    // Check to see if our last midpoint is a start point beyond the line break.  If so,
-    // shave it off the list, and shave off a trailing space if the previous end point doesn't
-    // preserve whitespace.
-    if (lBreak.m_obj && lineMidpointState.numMidpoints && !(lineMidpointState.numMidpoints % 2)) {
-        InlineIterator* midpoints = lineMidpointState.midpoints.data();
-        InlineIterator& endpoint = midpoints[lineMidpointState.numMidpoints - 2];
-        const InlineIterator& startpoint = midpoints[lineMidpointState.numMidpoints - 1];
-        InlineIterator currpoint = endpoint;
-        while (!currpoint.atEnd() && currpoint != startpoint && currpoint != lBreak)
-            currpoint.increment();
-        if (currpoint == lBreak) {
-            // We hit the line break before the start point.  Shave off the start point.
-            lineMidpointState.numMidpoints--;
-            if (endpoint.m_obj->style()->collapseWhiteSpace() && endpoint.m_obj->isText())
-                endpoint.m_pos--;
-        }
-    }
-}
-
-// Don't call this directly. Use one of the descriptive helper functions below.
-static void deprecatedAddMidpoint(LineMidpointState& lineMidpointState, const InlineIterator& midpoint)
-{
-    if (lineMidpointState.midpoints.size() <= lineMidpointState.numMidpoints)
-        lineMidpointState.midpoints.grow(lineMidpointState.numMidpoints + 10);
-
-    InlineIterator* midpoints = lineMidpointState.midpoints.data();
-    midpoints[lineMidpointState.numMidpoints++] = midpoint;
-}
-
-static inline void startIgnoringSpaces(LineMidpointState& lineMidpointState, const InlineIterator& midpoint)
-{
-    ASSERT(!(lineMidpointState.numMidpoints % 2));
-    deprecatedAddMidpoint(lineMidpointState, midpoint);
-}
-
-static inline void stopIgnoringSpaces(LineMidpointState& lineMidpointState, const InlineIterator& midpoint)
-{
-    ASSERT(lineMidpointState.numMidpoints % 2);
-    deprecatedAddMidpoint(lineMidpointState, midpoint);
+    return new BidiRun(start, end, obj, resolver.context(), resolver.dir());
 }
 
-// When ignoring spaces, this needs to be called for objects that need line boxes such as RenderInlines or
-// hard line breaks to ensure that they're not ignored.
-static inline void ensureLineBoxInsideIgnoredSpaces(LineMidpointState& lineMidpointState, RenderObject* renderer)
-{
-    InlineIterator midpoint(0, renderer, 0);
-    stopIgnoringSpaces(lineMidpointState, midpoint);
-    startIgnoringSpaces(lineMidpointState, midpoint);
-}
-
-// Adding a pair of midpoints before a character will split it out into a new line box.
-static inline void ensureCharacterGetsLineBox(LineMidpointState& lineMidpointState, InlineIterator& textParagraphSeparator)
-{
-    InlineIterator midpoint(0, textParagraphSeparator.m_obj, textParagraphSeparator.m_pos);
-    startIgnoringSpaces(lineMidpointState, InlineIterator(0, textParagraphSeparator.m_obj, textParagraphSeparator.m_pos - 1));
-    stopIgnoringSpaces(lineMidpointState, InlineIterator(0, textParagraphSeparator.m_obj, textParagraphSeparator.m_pos));
-}
-
-static inline BidiRun* createRun(int start, int end, RenderObject* obj, InlineBidiResolver& resolver)
-{
-    return new (obj->renderArena()) BidiRun(start, end, obj, resolver.context(), resolver.dir());
-}
-
-void RenderBlock::appendRunsForObject(BidiRunList<BidiRun>& runs, int start, int end, RenderObject* obj, InlineBidiResolver& resolver)
+void RenderBlockFlow::appendRunsForObject(BidiRunList<BidiRun>* runs, int start, int end, RenderObject& obj, InlineBidiResolver& resolver)
 {
     if (start > end || shouldSkipCreatingRunsForObject(obj))
         return;
 
     LineMidpointState& lineMidpointState = resolver.midpointState();
-    bool haveNextMidpoint = (lineMidpointState.currentMidpoint < lineMidpointState.numMidpoints);
+    bool haveNextMidpoint = (lineMidpointState.currentMidpoint() < lineMidpointState.numMidpoints());
     InlineIterator nextMidpoint;
     if (haveNextMidpoint)
-        nextMidpoint = lineMidpointState.midpoints[lineMidpointState.currentMidpoint];
-    if (lineMidpointState.betweenMidpoints) {
-        if (!(haveNextMidpoint && nextMidpoint.m_obj == obj))
+        nextMidpoint = lineMidpointState.midpoints()[lineMidpointState.currentMidpoint()];
+    if (lineMidpointState.betweenMidpoints()) {
+        if (!haveNextMidpoint || (&obj != nextMidpoint.renderer()))
             return;
         // This is a new start point. Stop ignoring objects and
         // adjust our start.
-        lineMidpointState.betweenMidpoints = false;
-        start = nextMidpoint.m_pos;
-        lineMidpointState.currentMidpoint++;
-        if (start < end)
-            return appendRunsForObject(runs, start, end, obj, resolver);
+        start = nextMidpoint.offset();
+        lineMidpointState.incrementCurrentMidpoint();
+        if (start < end) {
+            appendRunsForObject(runs, start, end, obj, resolver);
+            return;
+        }
     } else {
-        if (!haveNextMidpoint || (obj != nextMidpoint.m_obj)) {
-            runs.addRun(createRun(start, end, obj, resolver));
+        if (!haveNextMidpoint || (&obj != nextMidpoint.renderer())) {
+            if (runs)
+                runs->addRun(createRun(start, end, obj, resolver));
             return;
         }
 
-        // An end midpoint has been encountered within our object.  We
-        // need to go ahead and append a run with our endpoint.
-        if (static_cast<int>(nextMidpoint.m_pos + 1) <= end) {
-            lineMidpointState.betweenMidpoints = true;
-            lineMidpointState.currentMidpoint++;
-            if (nextMidpoint.m_pos != UINT_MAX) { // UINT_MAX means stop at the object and don't include any of it.
-                if (static_cast<int>(nextMidpoint.m_pos + 1) > start)
-                    runs.addRun(createRun(start, nextMidpoint.m_pos + 1, obj, resolver));
-                return appendRunsForObject(runs, nextMidpoint.m_pos + 1, end, obj, resolver);
-            }
-        } else
-           runs.addRun(createRun(start, end, obj, resolver));
+        // An end midpoint has been encountered within our object. We need to append a run with our endpoint.
+        if (static_cast<int>(nextMidpoint.offset() + 1) <= end) {
+            lineMidpointState.incrementCurrentMidpoint();
+            // The end of the line is before the object we're inspecting. Skip everything and return
+            if (nextMidpoint.refersToEndOfPreviousNode())
+                return;
+            if (static_cast<int>(nextMidpoint.offset() + 1) > start && runs)
+                runs->addRun(createRun(start, nextMidpoint.offset() + 1, obj, resolver));
+            appendRunsForObject(runs, nextMidpoint.offset() + 1, end, obj, resolver);
+        } else if (runs)
+            runs->addRun(createRun(start, end, obj, resolver));
     }
 }
 
-static inline InlineBox* createInlineBoxForRenderer(RenderObject* obj, bool isRootLineBox, bool isOnlyRun = false)
+std::unique_ptr<RootInlineBox> RenderBlockFlow::createRootInlineBox()
 {
-    if (isRootLineBox)
-        return toRenderBlock(obj)->createAndAppendRootInlineBox();
+    return std::make_unique<RootInlineBox>(*this);
+}
 
-    if (obj->isText()) {
-        InlineTextBox* textBox = toRenderText(obj)->createInlineTextBox();
-        // We only treat a box as text for a <br> if we are on a line by ourself or in strict mode
-        // (Note the use of strict mode.  In "almost strict" mode, we don't treat the box for <br> as text.)
-        if (obj->isBR())
-            textBox->setIsText(isOnlyRun || obj->document()->inNoQuirksMode());
-        return textBox;
-    }
+RootInlineBox* RenderBlockFlow::createAndAppendRootInlineBox()
+{
+    auto newRootBox = createRootInlineBox();
+    RootInlineBox* rootBox = newRootBox.get();
+    m_lineBoxes.appendLineBox(WTFMove(newRootBox));
 
-    if (obj->isBox())
-        return toRenderBox(obj)->createInlineBox();
+    if (UNLIKELY(AXObjectCache::accessibilityEnabled()) && firstRootBox() == rootBox) {
+        if (AXObjectCache* cache = document().existingAXObjectCache())
+            cache->recomputeIsIgnored(this);
+    }
 
-    return toRenderInline(obj)->createAndAppendInlineFlowBox();
+    return rootBox;
 }
 
-// FIXME: Don't let counters mark themselves as needing pref width recalcs during layout
-// so we don't need this hack.
-static inline void updateCounterIfNeeded(RenderText* o)
+static inline InlineBox* createInlineBoxForRenderer(RenderObject* renderer, bool isRootLineBox, bool isOnlyRun = false)
 {
-    if (!o->preferredLogicalWidthsDirty() || !o->isCounter())
-        return;
-    toRenderCounter(o)->updateCounter();
+    if (isRootLineBox)
+        return downcast<RenderBlockFlow>(*renderer).createAndAppendRootInlineBox();
+
+    if (is<RenderText>(*renderer))
+        return downcast<RenderText>(*renderer).createInlineTextBox();
+
+    if (is<RenderBox>(*renderer)) {
+        // FIXME: This is terrible. This branch returns an *owned* pointer!
+        return downcast<RenderBox>(*renderer).createInlineBox().release();
+    }
+
+    if (is<RenderLineBreak>(*renderer)) {
+        // FIXME: This is terrible. This branch returns an *owned* pointer!
+        auto inlineBox = downcast<RenderLineBreak>(*renderer).createInlineBox().release();
+        // We only treat a box as text for a <br> if we are on a line by ourself or in strict mode
+        // (Note the use of strict mode. In "almost strict" mode, we don't treat the box for <br> as text.)
+        inlineBox->setBehavesLikeText(isOnlyRun || renderer->document().inNoQuirksMode() || renderer->isLineBreakOpportunity());
+        return inlineBox;
+    }
+
+    return downcast<RenderInline>(*renderer).createAndAppendInlineFlowBox();
 }
 
-static inline void dirtyLineBoxesForRenderer(RenderObject* o, bool fullLayout)
+static inline void dirtyLineBoxesForRenderer(RenderObject& renderer, bool fullLayout)
 {
-    if (o->isText()) {
-        RenderText* renderText = toRenderText(o);
+    if (is<RenderText>(renderer)) {
+        RenderText& renderText = downcast<RenderText>(renderer);
         updateCounterIfNeeded(renderText);
-        renderText->dirtyLineBoxes(fullLayout);
-    } else
-        toRenderInline(o)->dirtyLineBoxes(fullLayout);
+        renderText.dirtyLineBoxes(fullLayout);
+    } else if (is<RenderLineBreak>(renderer))
+        downcast<RenderLineBreak>(renderer).dirtyLineBoxes(fullLayout);
+    else
+        downcast<RenderInline>(renderer).dirtyLineBoxes(fullLayout);
 }
 
 static bool parentIsConstructedOrHaveNext(InlineFlowBox* parentBox)
@@ -563,21 +184,21 @@ static bool parentIsConstructedOrHaveNext(InlineFlowBox* parentBox)
     return false;
 }
 
-InlineFlowBox* RenderBlock::createLineBoxes(RenderObject* obj, const LineInfo& lineInfo, InlineBox* childBox, bool startNewSegment)
+InlineFlowBox* RenderBlockFlow::createLineBoxes(RenderObject* obj, const LineInfo& lineInfo, InlineBox* childBox)
 {
     // See if we have an unconstructed line box for this object that is also
     // the last item on the line.
     unsigned lineDepth = 1;
-    InlineFlowBox* parentBox = 0;
-    InlineFlowBox* result = 0;
-    bool hasDefaultLineBoxContain = style()->lineBoxContain() == RenderStyle::initialLineBoxContain();
+    InlineFlowBox* parentBox = nullptr;
+    InlineFlowBox* result = nullptr;
+    bool hasDefaultLineBoxContain = style().lineBoxContain() == RenderStyle::initialLineBoxContain();
     do {
-        ASSERT_WITH_SECURITY_IMPLICATION(obj->isRenderInline() || obj == this);
+        ASSERT_WITH_SECURITY_IMPLICATION(is<RenderInline>(*obj) || obj == this);
 
-        RenderInline* inlineFlow = (obj != this) ? toRenderInline(obj) : 0;
+        RenderInline* inlineFlow = obj != this ? downcast<RenderInline>(obj) : nullptr;
 
         // Get the last box we made for this render object.
-        parentBox = inlineFlow ? inlineFlow->lastLineBox() : toRenderBlock(obj)->lastLineBox();
+        parentBox = inlineFlow ? inlineFlow->lastLineBox() : downcast<RenderBlockFlow>(*obj).lastRootBox();
 
         // If this box or its ancestor is constructed then it is from a previous line, and we need
         // to make a new box for our line.  If this box or its ancestor is unconstructed but it has
@@ -586,15 +207,13 @@ InlineFlowBox* RenderBlock::createLineBoxes(RenderObject* obj, const LineInfo& l
         // the same line (this can happen with very fancy language mixtures).
         bool constructedNewBox = false;
         bool allowedToConstructNewBox = !hasDefaultLineBoxContain || !inlineFlow || inlineFlow->alwaysCreateLineBoxes();
-        bool mustCreateBoxesToRoot = startNewSegment && !(parentBox && parentBox->isRootInlineBox());
-        bool canUseExistingParentBox = parentBox && !parentIsConstructedOrHaveNext(parentBox) && !mustCreateBoxesToRoot;
+        bool canUseExistingParentBox = parentBox && !parentIsConstructedOrHaveNext(parentBox);
         if (allowedToConstructNewBox && !canUseExistingParentBox) {
             // We need to make a new box for this render object.  Once
             // made, we need to place it at the end of the current line.
             InlineBox* newBox = createInlineBoxForRenderer(obj, obj == this);
-            ASSERT_WITH_SECURITY_IMPLICATION(newBox->isInlineFlowBox());
-            parentBox = toInlineFlowBox(newBox);
-            parentBox->setFirstLineStyleBit(lineInfo.isFirstLine());
+            parentBox = downcast<InlineFlowBox>(newBox);
+            parentBox->setIsFirstLine(lineInfo.isFirstLine());
             parentBox->setIsHorizontal(isHorizontalWritingMode());
             if (!hasDefaultLineBoxContain)
                 parentBox->clearDescendantsHaveSameLineHeightAndBaseline();
@@ -643,105 +262,130 @@ static bool reachedEndOfTextRenderer(const BidiRunList<BidiRun>& bidiRuns)
     if (!run)
         return true;
     unsigned pos = run->stop();
-    RenderObject* r = run->m_object;
-    if (!r->isText() || r->isBR())
+    const RenderObject& renderer = run->renderer();
+    if (!is<RenderText>(renderer))
         return false;
-    RenderText* renderText = toRenderText(r);
-    unsigned length = renderText->textLength();
+    const RenderText& renderText = downcast<RenderText>(renderer);
+    unsigned length = renderText.textLength();
     if (pos >= length)
         return true;
 
-    if (renderText->is8Bit())
-        return endsWithASCIISpaces(renderText->characters8(), pos, length);
-    return endsWithASCIISpaces(renderText->characters16(), pos, length);
+    if (renderText.is8Bit())
+        return endsWithASCIISpaces(renderText.characters8(), pos, length);
+    return endsWithASCIISpaces(renderText.characters16(), pos, length);
 }
 
-RootInlineBox* RenderBlock::constructLine(BidiRunList<BidiRun>& bidiRuns, const LineInfo& lineInfo)
+RootInlineBox* RenderBlockFlow::constructLine(BidiRunList<BidiRun>& bidiRuns, const LineInfo& lineInfo)
 {
     ASSERT(bidiRuns.firstRun());
 
     bool rootHasSelectedChildren = false;
     InlineFlowBox* parentBox = 0;
     int runCount = bidiRuns.runCount() - lineInfo.runsFromLeadingWhitespace();
+    
     for (BidiRun* r = bidiRuns.firstRun(); r; r = r->next()) {
         // Create a box for our object.
         bool isOnlyRun = (runCount == 1);
-        if (runCount == 2 && !r->m_object->isListMarker())
-            isOnlyRun = (!style()->isLeftToRightDirection() ? bidiRuns.lastRun() : bidiRuns.firstRun())->m_object->isListMarker();
+        if (runCount == 2 && !r->renderer().isListMarker())
+            isOnlyRun = (!style().isLeftToRightDirection() ? bidiRuns.lastRun() : bidiRuns.firstRun())->renderer().isListMarker();
 
         if (lineInfo.isEmpty())
             continue;
 
-        InlineBox* box = createInlineBoxForRenderer(r->m_object, false, isOnlyRun);
-        r->m_box = box;
-
-        ASSERT(box);
-        if (!box)
-            continue;
+        InlineBox* box = createInlineBoxForRenderer(&r->renderer(), false, isOnlyRun);
+        r->setBox(box);
 
-        if (!rootHasSelectedChildren && box->renderer()->selectionState() != RenderObject::SelectionNone)
+        if (!rootHasSelectedChildren && box->renderer().selectionState() != RenderObject::SelectionNone)
             rootHasSelectedChildren = true;
-
+        
         // If we have no parent box yet, or if the run is not simply a sibling,
         // then we need to construct inline boxes as necessary to properly enclose the
         // run's inline box. Segments can only be siblings at the root level, as
         // they are positioned separately.
-#if ENABLE(CSS_SHAPES)
-        bool runStartsSegment = r->m_startsSegment;
-#else
-        bool runStartsSegment = false;
-#endif
-        if (!parentBox || parentBox->renderer() != r->m_object->parent() || runStartsSegment)
+        if (!parentBox || &parentBox->renderer() != r->renderer().parent()) {
             // Create new inline boxes all the way back to the appropriate insertion point.
-            parentBox = createLineBoxes(r->m_object->parent(), lineInfo, box, runStartsSegment);
-        else {
+            RenderObject* parentToUse = r->renderer().parent();
+            parentBox = createLineBoxes(parentToUse, lineInfo, box);
+        } else {
             // Append the inline box to this line.
             parentBox->addToLine(box);
         }
 
-        bool visuallyOrdered = r->m_object->style()->rtlOrdering() == VisualOrder;
+        bool visuallyOrdered = r->renderer().style().rtlOrdering() == VisualOrder;
         box->setBidiLevel(r->level());
 
-        if (box->isInlineTextBox()) {
-            InlineTextBox* text = toInlineTextBox(box);
-            text->setStart(r->m_start);
-            text->setLen(r->m_stop - r->m_start);
-            text->setDirOverride(r->dirOverride(visuallyOrdered));
+        if (is<InlineTextBox>(*box)) {
+            auto& textBox = downcast<InlineTextBox>(*box);
+            textBox.setStart(r->m_start);
+            textBox.setLen(r->m_stop - r->m_start);
+            textBox.setDirOverride(r->dirOverride(visuallyOrdered));
             if (r->m_hasHyphen)
-                text->setHasHyphen(true);
+                textBox.setHasHyphen(true);
         }
     }
 
     // We should have a root inline box.  It should be unconstructed and
     // be the last continuation of our line list.
-    ASSERT(lastLineBox() && !lastLineBox()->isConstructed());
+    ASSERT(lastRootBox() && !lastRootBox()->isConstructed());
 
     // Set the m_selectedChildren flag on the root inline box if one of the leaf inline box
     // from the bidi runs walk above has a selection state.
     if (rootHasSelectedChildren)
-        lastLineBox()->root()->setHasSelectedChildren(true);
+        lastRootBox()->root().setHasSelectedChildren(true);
 
     // Set bits on our inline flow boxes that indicate which sides should
     // paint borders/margins/padding.  This knowledge will ultimately be used when
     // we determine the horizontal positions and widths of all the inline boxes on
     // the line.
-    bool isLogicallyLastRunWrapped = bidiRuns.logicallyLastRun()->m_object && bidiRuns.logicallyLastRun()->m_object->isText() ? !reachedEndOfTextRenderer(bidiRuns) : true;
-    lastLineBox()->determineSpacingForFlowBoxes(lineInfo.isLastLine(), isLogicallyLastRunWrapped, bidiRuns.logicallyLastRun()->m_object);
+    bool isLogicallyLastRunWrapped = bidiRuns.logicallyLastRun()->renderer().isText() ? !reachedEndOfTextRenderer(bidiRuns) : true;
+    lastRootBox()->determineSpacingForFlowBoxes(lineInfo.isLastLine(), isLogicallyLastRunWrapped, &bidiRuns.logicallyLastRun()->renderer());
 
     // Now mark the line boxes as being constructed.
-    lastLineBox()->setConstructed();
+    lastRootBox()->setConstructed();
 
     // Return the last line.
     return lastRootBox();
 }
 
-ETextAlign RenderBlock::textAlignmentForLine(bool endsWithSoftBreak) const
+ETextAlign RenderBlockFlow::textAlignmentForLine(bool endsWithSoftBreak) const
 {
-    ETextAlign alignment = style()->textAlign();
-    if (!endsWithSoftBreak && alignment == JUSTIFY)
-        alignment = TASTART;
+    ETextAlign alignment = style().textAlign();
+#if ENABLE(CSS3_TEXT)
+    TextJustify textJustify = style().textJustify();
+    if (alignment == JUSTIFY && textJustify == TextJustifyNone)
+        return style().direction() == LTR ? LEFT : RIGHT;
+#endif
+
+    if (endsWithSoftBreak)
+        return alignment;
 
+#if !ENABLE(CSS3_TEXT)
+    return (alignment == JUSTIFY) ? TASTART : alignment;
+#else
+    if (alignment != JUSTIFY)
+        return alignment;
+
+    TextAlignLast alignmentLast = style().textAlignLast();
+    switch (alignmentLast) {
+    case TextAlignLastStart:
+        return TASTART;
+    case TextAlignLastEnd:
+        return TAEND;
+    case TextAlignLastLeft:
+        return LEFT;
+    case TextAlignLastRight:
+        return RIGHT;
+    case TextAlignLastCenter:
+        return CENTER;
+    case TextAlignLastJustify:
+        return JUSTIFY;
+    case TextAlignLastAuto:
+        if (textJustify == TextJustifyDistribute)
+            return JUSTIFY;
+        return TASTART;
+    }
     return alignment;
+#endif
 }
 
 static void updateLogicalWidthForLeftAlignedBlock(bool isLeftToRightDirection, BidiRun* trailingSpaceRun, float& logicalLeft, float& totalLogicalWidth, float availableLogicalWidth)
@@ -750,12 +394,12 @@ static void updateLogicalWidthForLeftAlignedBlock(bool isLeftToRightDirection, B
     // In particular with RTL blocks, wide lines should still spill out to the left.
     if (isLeftToRightDirection) {
         if (totalLogicalWidth > availableLogicalWidth && trailingSpaceRun)
-            trailingSpaceRun->m_box->setLogicalWidth(max<float>(0, trailingSpaceRun->m_box->logicalWidth() - totalLogicalWidth + availableLogicalWidth));
+            trailingSpaceRun->box()->setLogicalWidth(std::max<float>(0, trailingSpaceRun->box()->logicalWidth() - totalLogicalWidth + availableLogicalWidth));
         return;
     }
 
     if (trailingSpaceRun)
-        trailingSpaceRun->m_box->setLogicalWidth(0);
+        trailingSpaceRun->box()->setLogicalWidth(0);
     else if (totalLogicalWidth > availableLogicalWidth)
         logicalLeft -= (totalLogicalWidth - availableLogicalWidth);
 }
@@ -767,17 +411,16 @@ static void updateLogicalWidthForRightAlignedBlock(bool isLeftToRightDirection,
     // side of the block.
     if (isLeftToRightDirection) {
         if (trailingSpaceRun) {
-            totalLogicalWidth -= trailingSpaceRun->m_box->logicalWidth();
-            trailingSpaceRun->m_box->setLogicalWidth(0);
+            totalLogicalWidth -= trailingSpaceRun->box()->logicalWidth();
+            trailingSpaceRun->box()->setLogicalWidth(0);
         }
-        if (totalLogicalWidth < availableLogicalWidth)
-            logicalLeft += availableLogicalWidth - totalLogicalWidth;
+        logicalLeft += std::max(0.f, availableLogicalWidth - totalLogicalWidth);
         return;
     }
 
     if (totalLogicalWidth > availableLogicalWidth && trailingSpaceRun) {
-        trailingSpaceRun->m_box->setLogicalWidth(max<float>(0, trailingSpaceRun->m_box->logicalWidth() - totalLogicalWidth + availableLogicalWidth));
-        totalLogicalWidth -= trailingSpaceRun->m_box->logicalWidth();
+        trailingSpaceRun->box()->setLogicalWidth(std::max<float>(0, trailingSpaceRun->box()->logicalWidth() - totalLogicalWidth + availableLogicalWidth));
+        totalLogicalWidth -= trailingSpaceRun->box()->logicalWidth();
     } else
         logicalLeft += availableLogicalWidth - totalLogicalWidth;
 }
@@ -786,68 +429,45 @@ static void updateLogicalWidthForCenterAlignedBlock(bool isLeftToRightDirection,
 {
     float trailingSpaceWidth = 0;
     if (trailingSpaceRun) {
-        totalLogicalWidth -= trailingSpaceRun->m_box->logicalWidth();
-        trailingSpaceWidth = min(trailingSpaceRun->m_box->logicalWidth(), (availableLogicalWidth - totalLogicalWidth + 1) / 2);
-        trailingSpaceRun->m_box->setLogicalWidth(max<float>(0, trailingSpaceWidth));
+        totalLogicalWidth -= trailingSpaceRun->box()->logicalWidth();
+        trailingSpaceWidth = std::min(trailingSpaceRun->box()->logicalWidth(), (availableLogicalWidth - totalLogicalWidth + 1) / 2);
+        trailingSpaceRun->box()->setLogicalWidth(std::max<float>(0, trailingSpaceWidth));
     }
     if (isLeftToRightDirection)
-        logicalLeft += max<float>((availableLogicalWidth - totalLogicalWidth) / 2, 0);
+        logicalLeft += std::max<float>((availableLogicalWidth - totalLogicalWidth) / 2, 0);
     else
         logicalLeft += totalLogicalWidth > availableLogicalWidth ? (availableLogicalWidth - totalLogicalWidth) : (availableLogicalWidth - totalLogicalWidth) / 2 - trailingSpaceWidth;
 }
 
-void RenderBlock::setMarginsForRubyRun(BidiRun* run, RenderRubyRun* renderer, RenderObject* previousObject, const LineInfo& lineInfo)
+void RenderBlockFlow::setMarginsForRubyRun(BidiRun* run, RenderRubyRun& renderer, RenderObject* previousObject, const LineInfo& lineInfo)
 {
-    int startOverhang;
-    int endOverhang;
+    float startOverhang;
+    float endOverhang;
     RenderObject* nextObject = 0;
     for (BidiRun* runWithNextObject = run->next(); runWithNextObject; runWithNextObject = runWithNextObject->next()) {
-        if (!runWithNextObject->m_object->isOutOfFlowPositioned() && !runWithNextObject->m_box->isLineBreak()) {
-            nextObject = runWithNextObject->m_object;
+        if (!runWithNextObject->renderer().isOutOfFlowPositioned() && !runWithNextObject->box()->isLineBreak()) {
+            nextObject = &runWithNextObject->renderer();
             break;
         }
     }
-    renderer->getOverhang(lineInfo.isFirstLine(), renderer->style()->isLeftToRightDirection() ? previousObject : nextObject, renderer->style()->isLeftToRightDirection() ? nextObject : previousObject, startOverhang, endOverhang);
+    renderer.getOverhang(lineInfo.isFirstLine(), renderer.style().isLeftToRightDirection() ? previousObject : nextObject, renderer.style().isLeftToRightDirection() ? nextObject : previousObject, startOverhang, endOverhang);
     setMarginStartForChild(renderer, -startOverhang);
     setMarginEndForChild(renderer, -endOverhang);
 }
 
-static inline float measureHyphenWidth(RenderText* renderer, const Font& font, HashSet<const SimpleFontData*>* fallbackFonts = 0)
-{
-    RenderStyle* style = renderer->style();
-    return font.width(RenderBlock::constructTextRun(renderer, font, style->hyphenString().string(), style), fallbackFonts);
-}
-
-class WordMeasurement {
-public:
-    WordMeasurement()
-        : renderer(0)
-        , width(0)
-        , startOffset(0)
-        , endOffset(0)
-    {
-    }
-    
-    RenderText* renderer;
-    float width;
-    int startOffset;
-    int endOffset;
-    HashSet<const SimpleFontData*> fallbackFonts;
-};
-
-static inline void setLogicalWidthForTextRun(RootInlineBox* lineBox, BidiRun* run, RenderText* renderer, float xPos, const LineInfo& lineInfo,
+static inline void setLogicalWidthForTextRun(RootInlineBox* lineBox, BidiRun* run, RenderText& renderer, float xPos, const LineInfo& lineInfo,
     GlyphOverflowAndFallbackFontsMap& textBoxDataMap, VerticalPositionCache& verticalPositionCache, WordMeasurements& wordMeasurements)
 {
-    HashSet<const SimpleFontData*> fallbackFonts;
+    HashSet<const Font*> fallbackFonts;
     GlyphOverflow glyphOverflow;
-    
-    const Font& font = renderer->style(lineInfo.isFirstLine())->font();
+
+    const FontCascade& font = lineStyle(*renderer.parent(), lineInfo).fontCascade();
     // Always compute glyph overflow if the block's line-box-contain value is "glyphs".
     if (lineBox->fitsToGlyphs()) {
         // If we don't stick out of the root line's font box, then don't bother computing our glyph overflow. This optimization
         // will keep us from computing glyph bounds in nearly all cases.
         bool includeRootLine = lineBox->includesRootLineBoxFontOrLeading();
-        int baselineShift = lineBox->verticalPositionForBox(run->m_box, verticalPositionCache);
+        int baselineShift = lineBox->verticalPositionForBox(run->box(), verticalPositionCache);
         int rootDescent = includeRootLine ? font.fontMetrics().descent() : 0;
         int rootAscent = includeRootLine ? font.fontMetrics().ascent() : 0;
         int boxAscent = font.fontMetrics().ascent() - baselineShift;
@@ -857,14 +477,13 @@ static inline void setLogicalWidthForTextRun(RootInlineBox* lineBox, BidiRun* ru
     }
     
     LayoutUnit hyphenWidth = 0;
-    if (toInlineTextBox(run->m_box)->hasHyphen()) {
-        const Font& font = renderer->style(lineInfo.isFirstLine())->font();
+    if (downcast<InlineTextBox>(*run->box()).hasHyphen())
         hyphenWidth = measureHyphenWidth(renderer, font, &fallbackFonts);
-    }
+
     float measuredWidth = 0;
 
-    bool kerningIsEnabled = font.typesettingFeatures() & Kerning;
-    bool canUseSimpleFontCodePath = renderer->canUseSimpleFontCodePath();
+    bool kerningIsEnabled = font.enableKerning();
+    bool canUseSimpleFontCodePath = renderer.canUseSimpleFontCodePath();
     
     // Since we don't cache glyph overflows, we need to re-measure the run if
     // the style is linebox-contain: glyph.
@@ -875,23 +494,23 @@ static inline void setLogicalWidthForTextRun(RootInlineBox* lineBox, BidiRun* ru
             WordMeasurement& wordMeasurement = wordMeasurements[i];
             if (wordMeasurement.width <= 0 || wordMeasurement.startOffset == wordMeasurement.endOffset)
                 continue;
-            if (wordMeasurement.renderer != renderer || wordMeasurement.startOffset != lastEndOffset || wordMeasurement.endOffset > run->m_stop)
+            if (wordMeasurement.renderer != &renderer || wordMeasurement.startOffset != lastEndOffset || wordMeasurement.endOffset > run->m_stop)
                 continue;
 
             lastEndOffset = wordMeasurement.endOffset;
             if (kerningIsEnabled && lastEndOffset == run->m_stop) {
                 int wordLength = lastEndOffset - wordMeasurement.startOffset;
                 GlyphOverflow overflow;
-                measuredWidth += renderer->width(wordMeasurement.startOffset, wordLength, xPos + measuredWidth, lineInfo.isFirstLine(),
+                measuredWidth += renderer.width(wordMeasurement.startOffset, wordLength, xPos + measuredWidth, lineInfo.isFirstLine(),
                     &wordMeasurement.fallbackFonts, &overflow);
-                UChar c = renderer->characterAt(wordMeasurement.startOffset);
+                UChar c = renderer.characterAt(wordMeasurement.startOffset);
                 if (i > 0 && wordLength == 1 && (c == ' ' || c == '\t'))
-                    measuredWidth += renderer->style()->wordSpacing();
+                    measuredWidth += renderer.style().fontCascade().wordSpacing();
             } else
                 measuredWidth += wordMeasurement.width;
             if (!wordMeasurement.fallbackFonts.isEmpty()) {
-                HashSet<const SimpleFontData*>::const_iterator end = wordMeasurement.fallbackFonts.end();
-                for (HashSet<const SimpleFontData*>::const_iterator it = wordMeasurement.fallbackFonts.begin(); it != end; ++it)
+                HashSet<const Font*>::const_iterator end = wordMeasurement.fallbackFonts.end();
+                for (HashSet<const Font*>::const_iterator it = wordMeasurement.fallbackFonts.begin(); it != end; ++it)
                     fallbackFonts.add(*it);
             }
         }
@@ -903,60 +522,114 @@ static inline void setLogicalWidthForTextRun(RootInlineBox* lineBox, BidiRun* ru
     }
 
     if (!measuredWidth)
-        measuredWidth = renderer->width(run->m_start, run->m_stop - run->m_start, xPos, lineInfo.isFirstLine(), &fallbackFonts, &glyphOverflow);
+        measuredWidth = renderer.width(run->m_start, run->m_stop - run->m_start, xPos, lineInfo.isFirstLine(), &fallbackFonts, &glyphOverflow);
 
-    run->m_box->setLogicalWidth(measuredWidth + hyphenWidth);
+    run->box()->setLogicalWidth(measuredWidth + hyphenWidth);
     if (!fallbackFonts.isEmpty()) {
-        ASSERT(run->m_box->isText());
-        GlyphOverflowAndFallbackFontsMap::iterator it = textBoxDataMap.add(toInlineTextBox(run->m_box), make_pair(Vector<const SimpleFontData*>(), GlyphOverflow())).iterator;
+        ASSERT(run->box()->behavesLikeText());
+        GlyphOverflowAndFallbackFontsMap::iterator it = textBoxDataMap.add(downcast<InlineTextBox>(run->box()), std::make_pair(Vector<const Font*>(), GlyphOverflow())).iterator;
         ASSERT(it->value.first.isEmpty());
         copyToVector(fallbackFonts, it->value.first);
-        run->m_box->parent()->clearDescendantsHaveSameLineHeightAndBaseline();
+        run->box()->parent()->clearDescendantsHaveSameLineHeightAndBaseline();
     }
-    if ((glyphOverflow.top || glyphOverflow.bottom || glyphOverflow.left || glyphOverflow.right)) {
-        ASSERT(run->m_box->isText());
-        GlyphOverflowAndFallbackFontsMap::iterator it = textBoxDataMap.add(toInlineTextBox(run->m_box), make_pair(Vector<const SimpleFontData*>(), GlyphOverflow())).iterator;
+
+    // Include text decoration visual overflow as part of the glyph overflow.
+    if (renderer.style().textDecorationsInEffect() != TextDecorationNone)
+        glyphOverflow.extendTo(visualOverflowForDecorations(run->box()->lineStyle(), downcast<InlineTextBox>(run->box())));
+
+    if (!glyphOverflow.isEmpty()) {
+        ASSERT(run->box()->behavesLikeText());
+        GlyphOverflowAndFallbackFontsMap::iterator it = textBoxDataMap.add(downcast<InlineTextBox>(run->box()), std::make_pair(Vector<const Font*>(), GlyphOverflow())).iterator;
         it->value.second = glyphOverflow;
-        run->m_box->clearKnownToHaveNoOverflow();
+        run->box()->clearKnownToHaveNoOverflow();
     }
 }
 
-static inline void computeExpansionForJustifiedText(BidiRun* firstRun, BidiRun* trailingSpaceRun, Vector<unsigned, 16>& expansionOpportunities, unsigned expansionOpportunityCount, float& totalLogicalWidth, float availableLogicalWidth)
+void RenderBlockFlow::updateRubyForJustifiedText(RenderRubyRun& rubyRun, BidiRun& r, const Vector<unsigned, 16>& expansionOpportunities, unsigned& expansionOpportunityCount, float& totalLogicalWidth, float availableLogicalWidth, size_t& i)
+{
+    if (!rubyRun.rubyBase() || !rubyRun.rubyBase()->firstRootBox() || rubyRun.rubyBase()->firstRootBox()->nextRootBox() || !r.renderer().style().collapseWhiteSpace())
+        return;
+
+    auto& rubyBase = *rubyRun.rubyBase();
+    auto& rootBox = *rubyBase.firstRootBox();
+
+    float totalExpansion = 0;
+    unsigned totalOpportunitiesInRun = 0;
+    for (auto* leafChild = rootBox.firstLeafChild(); leafChild; leafChild = leafChild->nextLeafChild()) {
+        if (!leafChild->isInlineTextBox())
+            continue;
+
+        unsigned opportunitiesInRun = expansionOpportunities[i++];
+        ASSERT(opportunitiesInRun <= expansionOpportunityCount);
+        auto expansion = (availableLogicalWidth - totalLogicalWidth) * opportunitiesInRun / expansionOpportunityCount;
+        totalExpansion += expansion;
+        totalOpportunitiesInRun += opportunitiesInRun;
+    }
+
+    ASSERT(!rubyRun.hasOverrideLogicalContentWidth());
+    float newBaseWidth = rubyRun.logicalWidth() + totalExpansion + marginStartForChild(rubyRun) + marginEndForChild(rubyRun);
+    float newRubyRunWidth = rubyRun.logicalWidth() + totalExpansion;
+    rubyBase.setInitialOffset((newRubyRunWidth - newBaseWidth) / 2);
+    rubyRun.setOverrideLogicalContentWidth(newRubyRunWidth);
+    rubyRun.setNeedsLayout(MarkOnlyThis);
+    rootBox.markDirty();
+    if (RenderRubyText* rubyText = rubyRun.rubyText()) {
+        if (RootInlineBox* textRootBox = rubyText->firstRootBox())
+            textRootBox->markDirty();
+    }
+    rubyRun.layoutBlock(true);
+    rubyRun.clearOverrideLogicalContentWidth();
+    r.box()->setExpansion(newRubyRunWidth - r.box()->logicalWidth());
+
+    // This relayout caused the size of the RenderRubyText and the RenderRubyBase to change, dependent on the line's current expansion. Next time we relayout the
+    // RenderRubyRun, make sure that we relayout the RenderRubyBase and RenderRubyText as well.
+    rubyBase.setNeedsLayout(MarkOnlyThis);
+    if (RenderRubyText* rubyText = rubyRun.rubyText())
+        rubyText->setNeedsLayout(MarkOnlyThis);
+
+    totalLogicalWidth += totalExpansion;
+    expansionOpportunityCount -= totalOpportunitiesInRun;
+}
+
+void RenderBlockFlow::computeExpansionForJustifiedText(BidiRun* firstRun, BidiRun* trailingSpaceRun, const Vector<unsigned, 16>& expansionOpportunities, unsigned expansionOpportunityCount, float totalLogicalWidth, float availableLogicalWidth)
 {
     if (!expansionOpportunityCount || availableLogicalWidth <= totalLogicalWidth)
         return;
 
     size_t i = 0;
-    for (BidiRun* r = firstRun; r; r = r->next()) {
-#if ENABLE(CSS_SHAPES)
-        // This method is called once per segment, do not move past the current segment.
-        if (r->m_startsSegment)
-            break;
-#endif
-        if (!r->m_box || r == trailingSpaceRun)
+    for (BidiRun* run = firstRun; run; run = run->next()) {
+        if (!run->box() || run == trailingSpaceRun)
             continue;
         
-        if (r->m_object->isText()) {
+        if (is<RenderText>(run->renderer())) {
             unsigned opportunitiesInRun = expansionOpportunities[i++];
             
             ASSERT(opportunitiesInRun <= expansionOpportunityCount);
             
             // Only justify text if whitespace is collapsed.
-            if (r->m_object->style()->collapseWhiteSpace()) {
-                InlineTextBox* textBox = toInlineTextBox(r->m_box);
-                int expansion = (availableLogicalWidth - totalLogicalWidth) * opportunitiesInRun / expansionOpportunityCount;
-                textBox->setExpansion(expansion);
+            if (run->renderer().style().collapseWhiteSpace()) {
+                InlineTextBox& textBox = downcast<InlineTextBox>(*run->box());
+                float expansion = (availableLogicalWidth - totalLogicalWidth) * opportunitiesInRun / expansionOpportunityCount;
+                textBox.setExpansion(expansion);
                 totalLogicalWidth += expansion;
             }
             expansionOpportunityCount -= opportunitiesInRun;
-            if (!expansionOpportunityCount)
-                break;
-        }
+        } else if (is<RenderRubyRun>(run->renderer()))
+            updateRubyForJustifiedText(downcast<RenderRubyRun>(run->renderer()), *run, expansionOpportunities, expansionOpportunityCount, totalLogicalWidth, availableLogicalWidth, i);
+
+        if (!expansionOpportunityCount)
+            break;
     }
 }
 
-void RenderBlock::updateLogicalWidthForAlignment(const ETextAlign& textAlign, BidiRun* trailingSpaceRun, float& logicalLeft, float& totalLogicalWidth, float& availableLogicalWidth, int expansionOpportunityCount)
+void RenderBlockFlow::updateLogicalWidthForAlignment(const ETextAlign& textAlign, const RootInlineBox* rootInlineBox, BidiRun* trailingSpaceRun, float& logicalLeft, float& totalLogicalWidth, float& availableLogicalWidth, int expansionOpportunityCount)
 {
+    TextDirection direction;
+    if (rootInlineBox && style().unicodeBidi() == Plaintext)
+        direction = rootInlineBox->direction();
+    else
+        direction = style().direction();
+
     // Armed with the total width of the line (without justification),
     // we now examine our text-align property in order to determine where to position the
     // objects horizontally. The total width of the line can be increased if we end up
@@ -964,69 +637,56 @@ void RenderBlock::updateLogicalWidthForAlignment(const ETextAlign& textAlign, Bi
     switch (textAlign) {
     case LEFT:
     case WEBKIT_LEFT:
-        updateLogicalWidthForLeftAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
+        updateLogicalWidthForLeftAlignedBlock(style().isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
         break;
     case RIGHT:
     case WEBKIT_RIGHT:
-        updateLogicalWidthForRightAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
+        updateLogicalWidthForRightAlignedBlock(style().isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
         break;
     case CENTER:
     case WEBKIT_CENTER:
-        updateLogicalWidthForCenterAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
+        updateLogicalWidthForCenterAlignedBlock(style().isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
         break;
     case JUSTIFY:
         adjustInlineDirectionLineBounds(expansionOpportunityCount, logicalLeft, availableLogicalWidth);
         if (expansionOpportunityCount) {
             if (trailingSpaceRun) {
-                totalLogicalWidth -= trailingSpaceRun->m_box->logicalWidth();
-                trailingSpaceRun->m_box->setLogicalWidth(0);
+                totalLogicalWidth -= trailingSpaceRun->box()->logicalWidth();
+                trailingSpaceRun->box()->setLogicalWidth(0);
             }
             break;
         }
-        // Fall through
+        FALLTHROUGH;
     case TASTART:
-        if (style()->isLeftToRightDirection())
-            updateLogicalWidthForLeftAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
+        if (direction == LTR)
+            updateLogicalWidthForLeftAlignedBlock(style().isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
         else
-            updateLogicalWidthForRightAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
+            updateLogicalWidthForRightAlignedBlock(style().isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
         break;
     case TAEND:
-        if (style()->isLeftToRightDirection())
-            updateLogicalWidthForRightAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
+        if (direction == LTR)
+            updateLogicalWidthForRightAlignedBlock(style().isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
         else
-            updateLogicalWidthForLeftAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
+            updateLogicalWidthForLeftAlignedBlock(style().isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
         break;
     }
 }
 
-static IndentTextOrNot requiresIndent(bool isFirstLine, bool isAfterHardLineBreak, RenderStyle* style)
-{
-    IndentTextOrNot shouldIndentText = DoNotIndentText;
-    if (isFirstLine)
-        shouldIndentText = IndentText;
-#if ENABLE(CSS3_TEXT)
-    else if (isAfterHardLineBreak && style->textIndentLine() == TextIndentEachLine) 
-        shouldIndentText = IndentText;
-
-    if (style->textIndentType() == TextIndentHanging)
-        shouldIndentText = shouldIndentText == IndentText ? DoNotIndentText : IndentText;
-#else
-    UNUSED_PARAM(isAfterHardLineBreak);
-    UNUSED_PARAM(style);
-#endif
-    return shouldIndentText;
-}
-
-static void updateLogicalInlinePositions(RenderBlock* block, float& lineLogicalLeft, float& lineLogicalRight, float& availableLogicalWidth, bool firstLine, IndentTextOrNot shouldIndentText, LayoutUnit boxLogicalHeight)
+static void updateLogicalInlinePositions(RenderBlockFlow& block, float& lineLogicalLeft, float& lineLogicalRight, float& availableLogicalWidth, bool firstLine,
+    IndentTextOrNot shouldIndentText, LayoutUnit boxLogicalHeight, RootInlineBox* rootBox)
 {
-    LayoutUnit lineLogicalHeight = logicalHeightForLine(block, firstLine, boxLogicalHeight);
-    lineLogicalLeft = block->pixelSnappedLogicalLeftOffsetForLine(block->logicalHeight(), shouldIndentText == IndentText, lineLogicalHeight);
-    lineLogicalRight = block->pixelSnappedLogicalRightOffsetForLine(block->logicalHeight(), shouldIndentText == IndentText, lineLogicalHeight);
+    LayoutUnit lineLogicalHeight = block.minLineHeightForReplacedRenderer(firstLine, boxLogicalHeight);
+    if (rootBox->hasAnonymousInlineBlock()) {
+        lineLogicalLeft = block.logicalLeftOffsetForContent(block.logicalHeight());
+        lineLogicalRight = block.logicalRightOffsetForContent(block.logicalHeight());
+    } else {
+        lineLogicalLeft = block.logicalLeftOffsetForLine(block.logicalHeight(), shouldIndentText, lineLogicalHeight);
+        lineLogicalRight = block.logicalRightOffsetForLine(block.logicalHeight(), shouldIndentText, lineLogicalHeight);
+    }
     availableLogicalWidth = lineLogicalRight - lineLogicalLeft;
 }
 
-void RenderBlock::computeInlineDirectionPositionsForLine(RootInlineBox* lineBox, const LineInfo& lineInfo, BidiRun* firstRun, BidiRun* trailingSpaceRun, bool reachedEnd,
-                                                         GlyphOverflowAndFallbackFontsMap& textBoxDataMap, VerticalPositionCache& verticalPositionCache, WordMeasurements& wordMeasurements)
+void RenderBlockFlow::computeInlineDirectionPositionsForLine(RootInlineBox* lineBox, const LineInfo& lineInfo, BidiRun* firstRun, BidiRun* trailingSpaceRun, bool reachedEnd, GlyphOverflowAndFallbackFontsMap& textBoxDataMap, VerticalPositionCache& verticalPositionCache, WordMeasurements& wordMeasurements)
 {
     ETextAlign textAlign = textAlignmentForLine(!reachedEnd && !lineBox->endsWithBreak());
     
@@ -1040,109 +700,185 @@ void RenderBlock::computeInlineDirectionPositionsForLine(RootInlineBox* lineBox,
     float lineLogicalLeft;
     float lineLogicalRight;
     float availableLogicalWidth;
-    updateLogicalInlinePositions(this, lineLogicalLeft, lineLogicalRight, availableLogicalWidth, isFirstLine, shouldIndentText, 0);
+    updateLogicalInlinePositions(*this, lineLogicalLeft, lineLogicalRight, availableLogicalWidth, isFirstLine, shouldIndentText, 0, lineBox);
     bool needsWordSpacing;
-#if ENABLE(CSS_SHAPES)
-    ShapeInsideInfo* shapeInsideInfo = layoutShapeInsideInfo();
-    if (shapeInsideInfo && shapeInsideInfo->hasSegments()) {
-        BidiRun* segmentStart = firstRun;
-        const SegmentList& segments = shapeInsideInfo->segments();
-        float logicalLeft = max<float>(roundToInt(segments[0].logicalLeft), lineLogicalLeft);
-        float logicalRight = min<float>(floorToInt(segments[0].logicalRight), lineLogicalRight);
-        float startLogicalLeft = logicalLeft;
-        float endLogicalRight = logicalLeft;
-        float minLogicalLeft = logicalLeft;
-        float maxLogicalRight = logicalLeft;
-        lineBox->beginPlacingBoxRangesInInlineDirection(logicalLeft);
-        for (size_t i = 0; i < segments.size(); i++) {
-            if (i) {
-                logicalLeft = max<float>(roundToInt(segments[i].logicalLeft), lineLogicalLeft);
-                logicalRight = min<float>(floorToInt(segments[i].logicalRight), lineLogicalRight);
-            }
-            availableLogicalWidth = logicalRight - logicalLeft;
-            BidiRun* newSegmentStart = computeInlineDirectionPositionsForSegment(lineBox, lineInfo, textAlign, logicalLeft, availableLogicalWidth, segmentStart, trailingSpaceRun, textBoxDataMap, verticalPositionCache, wordMeasurements);
-            needsWordSpacing = false;
-            endLogicalRight = lineBox->placeBoxRangeInInlineDirection(segmentStart->m_box, newSegmentStart ? newSegmentStart->m_box : 0, logicalLeft, minLogicalLeft, maxLogicalRight, needsWordSpacing, textBoxDataMap);
-            if (!newSegmentStart || !newSegmentStart->next())
-                break;
-            ASSERT(newSegmentStart->m_startsSegment);
-            // Discard the empty segment start marker bidi runs
-            segmentStart = newSegmentStart->next();
-        }
-        lineBox->endPlacingBoxRangesInInlineDirection(startLogicalLeft, endLogicalRight, minLogicalLeft, maxLogicalRight);
-        return;
-    }
-#endif
 
-    if (firstRun && firstRun->m_object->isReplaced()) {
-        RenderBox* renderBox = toRenderBox(firstRun->m_object);
-        updateLogicalInlinePositions(this, lineLogicalLeft, lineLogicalRight, availableLogicalWidth, isFirstLine, shouldIndentText, renderBox->logicalHeight());
+    if (firstRun && firstRun->renderer().isReplaced()) {
+        RenderBox& renderBox = downcast<RenderBox>(firstRun->renderer());
+        updateLogicalInlinePositions(*this, lineLogicalLeft, lineLogicalRight, availableLogicalWidth, isFirstLine, shouldIndentText, renderBox.logicalHeight(), lineBox);
     }
 
     computeInlineDirectionPositionsForSegment(lineBox, lineInfo, textAlign, lineLogicalLeft, availableLogicalWidth, firstRun, trailingSpaceRun, textBoxDataMap, verticalPositionCache, wordMeasurements);
     // The widths of all runs are now known. We can now place every inline box (and
     // compute accurate widths for the inline flow boxes).
     needsWordSpacing = false;
-    lineBox->placeBoxesInInlineDirection(lineLogicalLeft, needsWordSpacing, textBoxDataMap);
+    lineBox->placeBoxesInInlineDirection(lineLogicalLeft, needsWordSpacing);
+}
+
+static inline ExpansionBehavior expansionBehaviorForInlineTextBox(RenderBlockFlow& block, InlineTextBox& textBox, BidiRun* previousRun, BidiRun* nextRun, ETextAlign textAlign, bool isAfterExpansion)
+{
+    // Tatechuyoko is modeled as the Object Replacement Character (U+FFFC), which can never have expansion opportunities inside nor intrinsically adjacent to it.
+    if (textBox.renderer().style().textCombine() == TextCombineHorizontal)
+        return ForbidLeadingExpansion | ForbidTrailingExpansion;
+
+    ExpansionBehavior result = 0;
+    bool setLeadingExpansion = false;
+    bool setTrailingExpansion = false;
+    if (textAlign == JUSTIFY) {
+        // If the next box is ruby, and we're justifying, and the first box in the ruby base has a leading expansion, and we are a text box, then force a trailing expansion.
+        if (nextRun && is<RenderRubyRun>(nextRun->renderer()) && downcast<RenderRubyRun>(nextRun->renderer()).rubyBase() && nextRun->renderer().style().collapseWhiteSpace()) {
+            auto& rubyBase = *downcast<RenderRubyRun>(nextRun->renderer()).rubyBase();
+            if (rubyBase.firstRootBox() && !rubyBase.firstRootBox()->nextRootBox()) {
+                if (auto* leafChild = rubyBase.firstRootBox()->firstLeafChild()) {
+                    if (is<InlineTextBox>(*leafChild)) {
+                        // FIXME: This leadingExpansionOpportunity doesn't actually work because it doesn't perform the UBA
+                        if (FontCascade::leadingExpansionOpportunity(downcast<RenderText>(leafChild->renderer()).stringView(), leafChild->direction())) {
+                            setTrailingExpansion = true;
+                            result |= ForceTrailingExpansion;
+                        }
+                    }
+                }
+            }
+        }
+        // Same thing, except if we're following a ruby
+        if (previousRun && is<RenderRubyRun>(previousRun->renderer()) && downcast<RenderRubyRun>(previousRun->renderer()).rubyBase() && previousRun->renderer().style().collapseWhiteSpace()) {
+            auto& rubyBase = *downcast<RenderRubyRun>(previousRun->renderer()).rubyBase();
+            if (rubyBase.firstRootBox() && !rubyBase.firstRootBox()->nextRootBox()) {
+                if (auto* leafChild = rubyBase.firstRootBox()->lastLeafChild()) {
+                    if (is<InlineTextBox>(*leafChild)) {
+                        // FIXME: This leadingExpansionOpportunity doesn't actually work because it doesn't perform the UBA
+                        if (FontCascade::trailingExpansionOpportunity(downcast<RenderText>(leafChild->renderer()).stringView(), leafChild->direction())) {
+                            setLeadingExpansion = true;
+                            result |= ForceLeadingExpansion;
+                        }
+                    }
+                }
+            }
+        }
+        // If we're the first box inside a ruby base, forbid a leading expansion, and vice-versa
+        if (is<RenderRubyBase>(block)) {
+            RenderRubyBase& rubyBase = downcast<RenderRubyBase>(block);
+            if (&textBox == rubyBase.firstRootBox()->firstLeafChild()) {
+                setLeadingExpansion = true;
+                result |= ForbidLeadingExpansion;
+            } if (&textBox == rubyBase.firstRootBox()->lastLeafChild()) {
+                setTrailingExpansion = true;
+                result |= ForbidTrailingExpansion;
+            }
+        }
+    }
+    if (!setLeadingExpansion)
+        result |= isAfterExpansion ? ForbidLeadingExpansion : AllowLeadingExpansion;
+    if (!setTrailingExpansion)
+        result |= AllowTrailingExpansion;
+    return result;
 }
 
-BidiRun* RenderBlock::computeInlineDirectionPositionsForSegment(RootInlineBox* lineBox, const LineInfo& lineInfo, ETextAlign textAlign, float& logicalLeft, 
+static inline void applyExpansionBehavior(InlineTextBox& textBox, ExpansionBehavior expansionBehavior)
+{
+    switch (expansionBehavior & LeadingExpansionMask) {
+    case ForceLeadingExpansion:
+        textBox.setForceLeadingExpansion();
+        break;
+    case ForbidLeadingExpansion:
+        textBox.setCanHaveLeadingExpansion(false);
+        break;
+    case AllowLeadingExpansion:
+        textBox.setCanHaveLeadingExpansion(true);
+        break;
+    default:
+        ASSERT_NOT_REACHED();
+        break;
+    }
+    switch (expansionBehavior & TrailingExpansionMask) {
+    case ForceTrailingExpansion:
+        textBox.setForceTrailingExpansion();
+        break;
+    case ForbidTrailingExpansion:
+        textBox.setCanHaveTrailingExpansion(false);
+        break;
+    case AllowTrailingExpansion:
+        textBox.setCanHaveTrailingExpansion(true);
+        break;
+    default:
+        ASSERT_NOT_REACHED();
+        break;
+    }
+}
+
+BidiRun* RenderBlockFlow::computeInlineDirectionPositionsForSegment(RootInlineBox* lineBox, const LineInfo& lineInfo, ETextAlign textAlign, float& logicalLeft, 
     float& availableLogicalWidth, BidiRun* firstRun, BidiRun* trailingSpaceRun, GlyphOverflowAndFallbackFontsMap& textBoxDataMap, VerticalPositionCache& verticalPositionCache,
     WordMeasurements& wordMeasurements)
 {
     bool needsWordSpacing = false;
     float totalLogicalWidth = lineBox->getFlowSpacingLogicalWidth();
     unsigned expansionOpportunityCount = 0;
-    bool isAfterExpansion = true;
+    bool isAfterExpansion = is<RenderRubyBase>(*this) ? downcast<RenderRubyBase>(*this).isAfterExpansion() : true;
     Vector<unsigned, 16> expansionOpportunities;
-    RenderObject* previousObject = 0;
-
-    BidiRun* r = firstRun;
-    for (; r; r = r->next()) {
-#if ENABLE(CSS_SHAPES)
-        // Once we have reached the start of the next segment, we have finished
-        // computing the positions for this segment's contents.
-        if (r->m_startsSegment)
-            break;
-#endif
-        if (!r->m_box || r->m_object->isOutOfFlowPositioned() || r->m_box->isLineBreak())
+
+    BidiRun* run = firstRun;
+    BidiRun* previousRun = nullptr;
+    for (; run; run = run->next()) {
+        if (!run->box() || run->renderer().isOutOfFlowPositioned() || run->box()->isLineBreak()) {
             continue; // Positioned objects are only participating to figure out their
                       // correct static x position.  They have no effect on the width.
                       // Similarly, line break boxes have no effect on the width.
-        if (r->m_object->isText()) {
-            RenderText* rt = toRenderText(r->m_object);
-            if (textAlign == JUSTIFY && r != trailingSpaceRun) {
-                if (!isAfterExpansion)
-                    toInlineTextBox(r->m_box)->setCanHaveLeadingExpansion(true);
+        }
+        if (is<RenderText>(run->renderer())) {
+            auto& renderText = downcast<RenderText>(run->renderer());
+            auto& textBox = downcast<InlineTextBox>(*run->box());
+            if (textAlign == JUSTIFY && run != trailingSpaceRun) {
+                ExpansionBehavior expansionBehavior = expansionBehaviorForInlineTextBox(*this, textBox, previousRun, run->next(), textAlign, isAfterExpansion);
+                applyExpansionBehavior(textBox, expansionBehavior);
                 unsigned opportunitiesInRun;
-                if (rt->is8Bit())
-                    opportunitiesInRun = Font::expansionOpportunityCount(rt->characters8() + r->m_start, r->m_stop - r->m_start, r->m_box->direction(), isAfterExpansion);
-                else
-                    opportunitiesInRun = Font::expansionOpportunityCount(rt->characters16() + r->m_start, r->m_stop - r->m_start, r->m_box->direction(), isAfterExpansion);
+                std::tie(opportunitiesInRun, isAfterExpansion) = FontCascade::expansionOpportunityCount(renderText.stringView(run->m_start, run->m_stop), run->box()->direction(), expansionBehavior);
                 expansionOpportunities.append(opportunitiesInRun);
                 expansionOpportunityCount += opportunitiesInRun;
             }
 
-            if (int length = rt->textLength()) {
-                if (!r->m_start && needsWordSpacing && isSpaceOrNewline(rt->characterAt(r->m_start)))
-                    totalLogicalWidth += rt->style(lineInfo.isFirstLine())->font().wordSpacing();
-                needsWordSpacing = !isSpaceOrNewline(rt->characterAt(r->m_stop - 1)) && r->m_stop == length;
+            if (int length = renderText.textLength()) {
+                if (!run->m_start && needsWordSpacing && isSpaceOrNewline(renderText.characterAt(run->m_start)))
+                    totalLogicalWidth += lineStyle(*renderText.parent(), lineInfo).fontCascade().wordSpacing();
+                needsWordSpacing = !isSpaceOrNewline(renderText.characterAt(run->m_stop - 1)) && run->m_stop == length;
             }
 
-            setLogicalWidthForTextRun(lineBox, r, rt, totalLogicalWidth, lineInfo, textBoxDataMap, verticalPositionCache, wordMeasurements);
+            setLogicalWidthForTextRun(lineBox, run, renderText, totalLogicalWidth, lineInfo, textBoxDataMap, verticalPositionCache, wordMeasurements);
         } else {
-            isAfterExpansion = false;
-            if (!r->m_object->isRenderInline()) {
-                RenderBox* renderBox = toRenderBox(r->m_object);
-                if (renderBox->isRubyRun())
-                    setMarginsForRubyRun(r, toRenderRubyRun(renderBox), previousObject, lineInfo);
-                r->m_box->setLogicalWidth(logicalWidthForChild(renderBox));
+            bool encounteredJustifiedRuby = false;
+            if (is<RenderRubyRun>(run->renderer()) && textAlign == JUSTIFY && run != trailingSpaceRun && downcast<RenderRubyRun>(run->renderer()).rubyBase()) {
+                auto* rubyBase = downcast<RenderRubyRun>(run->renderer()).rubyBase();
+                if (rubyBase->firstRootBox() && !rubyBase->firstRootBox()->nextRootBox() && run->renderer().style().collapseWhiteSpace()) {
+                    rubyBase->setIsAfterExpansion(isAfterExpansion);
+                    for (auto* leafChild = rubyBase->firstRootBox()->firstLeafChild(); leafChild; leafChild = leafChild->nextLeafChild()) {
+                        if (!is<InlineTextBox>(*leafChild))
+                            continue;
+                        auto& textBox = downcast<InlineTextBox>(*leafChild);
+                        encounteredJustifiedRuby = true;
+                        auto& renderText = downcast<RenderText>(leafChild->renderer());
+                        ExpansionBehavior expansionBehavior = expansionBehaviorForInlineTextBox(*rubyBase, textBox, nullptr, nullptr, textAlign, isAfterExpansion);
+                        applyExpansionBehavior(textBox, expansionBehavior);
+                        unsigned opportunitiesInRun;
+                        std::tie(opportunitiesInRun, isAfterExpansion) = FontCascade::expansionOpportunityCount(renderText.stringView(), leafChild->direction(), expansionBehavior);
+                        expansionOpportunities.append(opportunitiesInRun);
+                        expansionOpportunityCount += opportunitiesInRun;
+                    }
+                }
+            }
+
+            if (!encounteredJustifiedRuby)
+                isAfterExpansion = false;
+
+            if (!is<RenderInline>(run->renderer())) {
+                auto& renderBox = downcast<RenderBox>(run->renderer());
+                if (is<RenderRubyRun>(renderBox))
+                    setMarginsForRubyRun(run, downcast<RenderRubyRun>(renderBox), previousRun ? &previousRun->renderer() : nullptr, lineInfo);
+                run->box()->setLogicalWidth(logicalWidthForChild(renderBox));
                 totalLogicalWidth += marginStartForChild(renderBox) + marginEndForChild(renderBox);
             }
         }
 
-        totalLogicalWidth += r->m_box->logicalWidth();
-        previousObject = r->m_object;
+        totalLogicalWidth += run->box()->logicalWidth();
+        previousRun = run;
     }
 
     if (isAfterExpansion && !expansionOpportunities.isEmpty()) {
@@ -1150,72 +886,93 @@ BidiRun* RenderBlock::computeInlineDirectionPositionsForSegment(RootInlineBox* l
         expansionOpportunityCount--;
     }
 
-    updateLogicalWidthForAlignment(textAlign, trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth, expansionOpportunityCount);
+    if (is<RenderRubyBase>(*this) && !expansionOpportunityCount)
+        textAlign = CENTER;
+
+    updateLogicalWidthForAlignment(textAlign, lineBox, trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth, expansionOpportunityCount);
 
     computeExpansionForJustifiedText(firstRun, trailingSpaceRun, expansionOpportunities, expansionOpportunityCount, totalLogicalWidth, availableLogicalWidth);
 
-    return r;
+    return run;
 }
 
-void RenderBlock::computeBlockDirectionPositionsForLine(RootInlineBox* lineBox, BidiRun* firstRun, GlyphOverflowAndFallbackFontsMap& textBoxDataMap,
+void RenderBlockFlow::removeInlineBox(BidiRun& run, const RootInlineBox& rootLineBox) const
+{
+    auto* inlineBox = run.box();
+#if !ASSERT_DISABLED
+    auto* inlineParent = inlineBox->parent();
+    while (inlineParent && inlineParent != &rootLineBox) {
+        ASSERT(!inlineParent->isDirty());
+        inlineParent = inlineParent->parent();
+    }
+    ASSERT(!rootLineBox.isDirty());
+#endif
+    auto* parent = inlineBox->parent();
+    inlineBox->removeFromParent();
+
+    auto& renderer = run.renderer();
+    if (is<RenderText>(renderer))
+        downcast<RenderText>(renderer).removeTextBox(downcast<InlineTextBox>(*inlineBox));
+    delete inlineBox;
+    run.setBox(nullptr);
+    // removeFromParent() unnecessarily dirties the ancestor subtree.
+    auto* ancestor = parent;
+    while (ancestor) {
+        ancestor->markDirty(false);
+        if (ancestor == &rootLineBox)
+            break;
+        ancestor = ancestor->parent();
+    }
+}
+
+void RenderBlockFlow::computeBlockDirectionPositionsForLine(RootInlineBox* lineBox, BidiRun* firstRun, GlyphOverflowAndFallbackFontsMap& textBoxDataMap,
                                                         VerticalPositionCache& verticalPositionCache)
 {
     setLogicalHeight(lineBox->alignBoxesInBlockDirection(logicalHeight(), textBoxDataMap, verticalPositionCache));
 
     // Now make sure we place replaced render objects correctly.
-    for (BidiRun* r = firstRun; r; r = r->next()) {
-        ASSERT(r->m_box);
-        if (!r->m_box)
+    for (auto* run = firstRun; run; run = run->next()) {
+        ASSERT(run->box());
+        if (!run->box())
             continue; // Skip runs with no line boxes.
 
         // Align positioned boxes with the top of the line box.  This is
         // a reasonable approximation of an appropriate y position.
-        if (r->m_object->isOutOfFlowPositioned())
-            r->m_box->setLogicalTop(logicalHeight());
+        auto& renderer = run->renderer();
+        if (renderer.isOutOfFlowPositioned())
+            run->box()->setLogicalTop(logicalHeight());
 
         // Position is used to properly position both replaced elements and
         // to update the static normal flow x/y of positioned elements.
-        if (r->m_object->isText())
-            toRenderText(r->m_object)->positionLineBox(r->m_box);
-        else if (r->m_object->isBox())
-            toRenderBox(r->m_object)->positionLineBox(r->m_box);
-    }
-    // Positioned objects and zero-length text nodes destroy their boxes in
-    // position(), which unnecessarily dirties the line.
-    lineBox->markDirty(false);
+        bool inlineBoxIsRedundant = false;
+        if (is<RenderText>(renderer)) {
+            auto& inlineTextBox = downcast<InlineTextBox>(*run->box());
+            downcast<RenderText>(renderer).positionLineBox(inlineTextBox);
+            inlineBoxIsRedundant = !inlineTextBox.len();
+        } else if (is<RenderBox>(renderer)) {
+            downcast<RenderBox>(renderer).positionLineBox(downcast<InlineElementBox>(*run->box()));
+            inlineBoxIsRedundant = renderer.isOutOfFlowPositioned();
+        } else if (is<RenderLineBreak>(renderer))
+            downcast<RenderLineBreak>(renderer).replaceInlineBoxWrapper(downcast<InlineElementBox>(*run->box()));
+        // Check if we need to keep this box on the line at all.
+        if (inlineBoxIsRedundant)
+            removeInlineBox(*run, *lineBox);
+    }
 }
 
-static inline bool isCollapsibleSpace(UChar character, RenderText* renderer)
+static inline bool isCollapsibleSpace(UChar character, const RenderText& renderer)
 {
     if (character == ' ' || character == '\t' || character == softHyphen)
         return true;
     if (character == '\n')
-        return !renderer->style()->preserveNewline();
+        return !renderer.style().preserveNewline();
     if (character == noBreakSpace)
-        return renderer->style()->nbspMode() == SPACE;
+        return renderer.style().nbspMode() == SPACE;
     return false;
 }
 
-
-static void setStaticPositions(RenderBlock* block, RenderBox* child)
-{
-    // FIXME: The math here is actually not really right. It's a best-guess approximation that
-    // will work for the common cases
-    RenderObject* containerBlock = child->container();
-    LayoutUnit blockHeight = block->logicalHeight();
-    if (containerBlock->isRenderInline()) {
-        // A relative positioned inline encloses us. In this case, we also have to determine our
-        // position as though we were an inline. Set |staticInlinePosition| and |staticBlockPosition| on the relative positioned
-        // inline so that we can obtain the value later.
-        toRenderInline(containerBlock)->layer()->setStaticInlinePosition(block->startAlignedOffsetForLine(blockHeight, false));
-        toRenderInline(containerBlock)->layer()->setStaticBlockPosition(blockHeight);
-    }
-    block->updateStaticInlinePositionForChild(child, blockHeight);
-    child->layer()->setStaticBlockPosition(blockHeight);
-}
-
 template <typename CharacterType>
-static inline int findFirstTrailingSpace(RenderText* lastText, const CharacterType* characters, int start, int stop)
+static inline int findFirstTrailingSpace(const RenderText& lastText, const CharacterType* characters, int start, int stop)
 {
     int firstSpace = stop;
     while (firstSpace > start) {
@@ -1228,36 +985,36 @@ static inline int findFirstTrailingSpace(RenderText* lastText, const CharacterTy
     return firstSpace;
 }
 
-inline BidiRun* RenderBlock::handleTrailingSpaces(BidiRunList<BidiRun>& bidiRuns, BidiContext* currentContext)
+inline BidiRun* RenderBlockFlow::handleTrailingSpaces(BidiRunList<BidiRun>& bidiRuns, BidiContext* currentContext)
 {
     if (!bidiRuns.runCount()
-        || !bidiRuns.logicallyLastRun()->m_object->style()->breakOnlyAfterWhiteSpace()
-        || !bidiRuns.logicallyLastRun()->m_object->style()->autoWrap())
-        return 0;
+        || !bidiRuns.logicallyLastRun()->renderer().style().breakOnlyAfterWhiteSpace()
+        || !bidiRuns.logicallyLastRun()->renderer().style().autoWrap())
+        return nullptr;
 
     BidiRun* trailingSpaceRun = bidiRuns.logicallyLastRun();
-    RenderObject* lastObject = trailingSpaceRun->m_object;
-    if (!lastObject->isText())
-        return 0;
+    const RenderObject& lastObject = trailingSpaceRun->renderer();
+    if (!is<RenderText>(lastObject))
+        return nullptr;
 
-    RenderText* lastText = toRenderText(lastObject);
+    const RenderText& lastText = downcast<RenderText>(lastObject);
     int firstSpace;
-    if (lastText->is8Bit())
-        firstSpace = findFirstTrailingSpace(lastText, lastText->characters8(), trailingSpaceRun->start(), trailingSpaceRun->stop());
+    if (lastText.is8Bit())
+        firstSpace = findFirstTrailingSpace(lastText, lastText.characters8(), trailingSpaceRun->start(), trailingSpaceRun->stop());
     else
-        firstSpace = findFirstTrailingSpace(lastText, lastText->characters16(), trailingSpaceRun->start(), trailingSpaceRun->stop());
+        firstSpace = findFirstTrailingSpace(lastText, lastText.characters16(), trailingSpaceRun->start(), trailingSpaceRun->stop());
 
     if (firstSpace == trailingSpaceRun->stop())
-        return 0;
+        return nullptr;
 
-    TextDirection direction = style()->direction();
+    TextDirection direction = style().direction();
     bool shouldReorder = trailingSpaceRun != (direction == LTR ? bidiRuns.lastRun() : bidiRuns.firstRun());
     if (firstSpace != trailingSpaceRun->start()) {
         BidiContext* baseContext = currentContext;
         while (BidiContext* parent = baseContext->parent())
             baseContext = parent;
 
-        BidiRun* newTrailingRun = new (renderArena()) BidiRun(firstSpace, trailingSpaceRun->m_stop, trailingSpaceRun->m_object, baseContext, OtherNeutral);
+        BidiRun* newTrailingRun = new BidiRun(firstSpace, trailingSpaceRun->m_stop, trailingSpaceRun->renderer(), baseContext, U_OTHER_NEUTRAL);
         trailingSpaceRun->m_stop = firstSpace;
         if (direction == LTR)
             bidiRuns.addRun(newTrailingRun);
@@ -1279,21 +1036,30 @@ inline BidiRun* RenderBlock::handleTrailingSpaces(BidiRunList<BidiRun>& bidiRuns
     return trailingSpaceRun;
 }
 
-void RenderBlock::appendFloatingObjectToLastLine(FloatingObject* floatingObject)
+void RenderBlockFlow::appendFloatingObjectToLastLine(FloatingObject* floatingObject)
 {
-    ASSERT(!floatingObject->m_originatingLine);
-    floatingObject->m_originatingLine = lastRootBox();
+    ASSERT_WITH_SECURITY_IMPLICATION(!floatingObject->originatingLine());
+    floatingObject->setOriginatingLine(lastRootBox());
     lastRootBox()->appendFloat(floatingObject->renderer());
 }
 
-// FIXME: This should be a BidiStatus constructor or create method.
-static inline BidiStatus statusWithDirection(TextDirection textDirection, bool isOverride)
+static inline void notifyResolverToResumeInIsolate(InlineBidiResolver& resolver, RenderObject* root, RenderObject* startObject)
 {
-    WTF::Unicode::Direction direction = textDirection == LTR ? LeftToRight : RightToLeft;
-    RefPtr<BidiContext> context = BidiContext::create(textDirection == LTR ? 0 : 1, direction, isOverride, FromStyleOrDOM);
+    if (root != startObject) {
+        RenderObject* parent = startObject->parent();
+        notifyResolverToResumeInIsolate(resolver, root, parent);
+        notifyObserverEnteredObject(&resolver, startObject);
+    }
+}
+
+static inline void setUpResolverToResumeInIsolate(InlineBidiResolver& resolver, InlineBidiResolver& topResolver, BidiRun& isolatedRun, RenderObject* root, RenderObject* startObject)
+{
+    // Set up m_midpointState
+    resolver.midpointState() = topResolver.midpointState();
+    resolver.midpointState().setCurrentMidpoint(topResolver.midpointForIsolatedRun(isolatedRun));
 
-    // This copies BidiStatus and may churn the ref on BidiContext. I doubt it matters.
-    return BidiStatus(direction, direction, direction, context.release());
+    // Set up m_nestedIsolateCount
+    notifyResolverToResumeInIsolate(resolver, root, startObject);
 }
 
 // FIXME: BidiResolver should have this logic.
@@ -1308,37 +1074,37 @@ static inline void constructBidiRunsForSegment(InlineBidiResolver& topResolver,
 
     while (!topResolver.isolatedRuns().isEmpty()) {
         // It does not matter which order we resolve the runs as long as we resolve them all.
-        BidiRun* isolatedRun = topResolver.isolatedRuns().last();
+        auto isolatedRun = WTFMove(topResolver.isolatedRuns().last());
         topResolver.isolatedRuns().removeLast();
+        currentRoot = &isolatedRun.root;
 
-        RenderObject* startObj = isolatedRun->object();
+        RenderObject& startObject = isolatedRun.object;
 
         // Only inlines make sense with unicode-bidi: isolate (blocks are already isolated).
         // FIXME: Because enterIsolate is not passed a RenderObject, we have to crawl up the
         // tree to see which parent inline is the isolate. We could change enterIsolate
         // to take a RenderObject and do this logic there, but that would be a layering
         // violation for BidiResolver (which knows nothing about RenderObject).
-        RenderInline* isolatedInline = toRenderInline(containingIsolate(startObj, currentRoot));
+        RenderInline* isolatedInline = downcast<RenderInline>(highestContainingIsolateWithinRoot(startObject, currentRoot));
+        ASSERT(isolatedInline);
+
         InlineBidiResolver isolatedResolver;
-        EUnicodeBidi unicodeBidi = isolatedInline->style()->unicodeBidi();
+        EUnicodeBidi unicodeBidi = isolatedInline->style().unicodeBidi();
         TextDirection direction;
         if (unicodeBidi == Plaintext)
-            determineDirectionality(direction, InlineIterator(isolatedInline, isolatedRun->object(), 0));
+            determineDirectionality(direction, InlineIterator(isolatedInline, &isolatedRun.object, 0));
         else {
             ASSERT(unicodeBidi == Isolate || unicodeBidi == IsolateOverride);
-            direction = isolatedInline->style()->direction();
+            direction = isolatedInline->style().direction();
         }
-        isolatedResolver.setStatus(statusWithDirection(direction, isOverride(unicodeBidi)));
+        isolatedResolver.setStatus(BidiStatus(direction, isOverride(unicodeBidi)));
 
-        // FIXME: The fact that we have to construct an Iterator here
-        // currently prevents this code from moving into BidiResolver.
-        if (!bidiFirstSkippingEmptyInlines(isolatedInline, &isolatedResolver))
-            continue;
+        setUpResolverToResumeInIsolate(isolatedResolver, topResolver, isolatedRun.runToReplace, isolatedInline, &startObject);
 
         // The starting position is the beginning of the first run within the isolate that was identified
         // during the earlier call to createBidiRunsForLine. This can be but is not necessarily the
         // first run within the isolate.
-        InlineIterator iter = InlineIterator(isolatedInline, startObj, isolatedRun->m_start);
+        InlineIterator iter = InlineIterator(isolatedInline, &startObject, isolatedRun.position);
         isolatedResolver.setPositionIgnoringNestedIsolates(iter);
 
         // We stop at the next end of line; we may re-enter this isolate in the next call to constructBidiRuns().
@@ -1350,73 +1116,36 @@ static inline void constructBidiRunsForSegment(InlineBidiResolver& topResolver,
         // itself to be turned into an InlineBox. We can't remove it here without potentially losing track of
         // the logically last run.
         if (isolatedResolver.runs().runCount())
-            bidiRuns.replaceRunWithRuns(isolatedRun, isolatedResolver.runs());
+            bidiRuns.replaceRunWithRuns(&isolatedRun.runToReplace, isolatedResolver.runs());
 
         // If we encountered any nested isolate runs, just move them
         // to the top resolver's list for later processing.
-        if (!isolatedResolver.isolatedRuns().isEmpty()) {
-            topResolver.isolatedRuns().appendVector(isolatedResolver.isolatedRuns());
-            isolatedResolver.isolatedRuns().clear();
-        }
-    }
-}
-
-static inline void constructBidiRunsForLine(const RenderBlock* block, InlineBidiResolver& topResolver, BidiRunList<BidiRun>& bidiRuns, const InlineIterator& endOfLine, VisualDirectionOverride override, bool previousLineBrokeCleanly)
-{
-#if !ENABLE(CSS_SHAPES)
-    UNUSED_PARAM(block);
-    constructBidiRunsForSegment(topResolver, bidiRuns, endOfLine, override, previousLineBrokeCleanly);
-#else
-    ShapeInsideInfo* shapeInsideInfo = block->layoutShapeInsideInfo();
-    if (!shapeInsideInfo || !shapeInsideInfo->hasSegments()) {
-        constructBidiRunsForSegment(topResolver, bidiRuns, endOfLine, override, previousLineBrokeCleanly);
-        return;
-    }
-
-    const SegmentRangeList& segmentRanges = shapeInsideInfo->segmentRanges();
-    ASSERT(segmentRanges.size());
-
-    for (size_t i = 0; i < segmentRanges.size(); i++) {
-        LineSegmentIterator iterator = segmentRanges[i].start;
-        InlineIterator segmentStart(iterator.root, iterator.object, iterator.offset);
-        iterator = segmentRanges[i].end;
-        InlineIterator segmentEnd(iterator.root, iterator.object, iterator.offset);
-        if (i) {
-            ASSERT(segmentStart.m_obj);
-            BidiRun* segmentMarker = createRun(segmentStart.m_pos, segmentStart.m_pos, segmentStart.m_obj, topResolver);
-            segmentMarker->m_startsSegment = true;
-            bidiRuns.addRun(segmentMarker);
-            // Do not collapse midpoints between segments
-            topResolver.midpointState().betweenMidpoints = false;
+        while (!isolatedResolver.isolatedRuns().isEmpty()) {
+            auto runWithContext = WTFMove(isolatedResolver.isolatedRuns().last());
+            isolatedResolver.isolatedRuns().removeLast();
+            topResolver.setMidpointForIsolatedRun(runWithContext.runToReplace, isolatedResolver.midpointForIsolatedRun(runWithContext.runToReplace));
+            topResolver.isolatedRuns().append(WTFMove(runWithContext));
         }
-        if (segmentStart == segmentEnd)
-            continue;
-        topResolver.setPosition(segmentStart, numberOfIsolateAncestors(segmentStart));
-        constructBidiRunsForSegment(topResolver, bidiRuns, segmentEnd, override, previousLineBrokeCleanly);
     }
-#endif
 }
 
 // This function constructs line boxes for all of the text runs in the resolver and computes their position.
-RootInlineBox* RenderBlock::createLineBoxesFromBidiRuns(BidiRunList<BidiRun>& bidiRuns, const InlineIterator& end, LineInfo& lineInfo, VerticalPositionCache& verticalPositionCache, BidiRun* trailingSpaceRun, WordMeasurements& wordMeasurements)
+RootInlineBox* RenderBlockFlow::createLineBoxesFromBidiRuns(unsigned bidiLevel, BidiRunList<BidiRun>& bidiRuns, const InlineIterator& end, LineInfo& lineInfo, VerticalPositionCache& verticalPositionCache, BidiRun* trailingSpaceRun, WordMeasurements& wordMeasurements)
 {
     if (!bidiRuns.runCount())
-        return 0;
+        return nullptr;
 
     // FIXME: Why is this only done when we had runs?
-    lineInfo.setLastLine(!end.m_obj);
+    lineInfo.setLastLine(!end.renderer());
 
     RootInlineBox* lineBox = constructLine(bidiRuns, lineInfo);
     if (!lineBox)
-        return 0;
+        return nullptr;
 
+    lineBox->setBidiLevel(bidiLevel);
     lineBox->setEndsWithBreak(lineInfo.previousLineBrokeCleanly());
     
-#if ENABLE(SVG)
-    bool isSVGRootInlineBox = lineBox->isSVGRootInlineBox();
-#else
-    bool isSVGRootInlineBox = false;
-#endif
+    bool isSVGRootInlineBox = is<SVGRootInlineBox>(*lineBox);
     
     GlyphOverflowAndFallbackFontsMap textBoxDataMap;
     
@@ -1427,136 +1156,43 @@ RootInlineBox* RenderBlock::createLineBoxesFromBidiRuns(BidiRunList<BidiRun>& bi
     // Now position our text runs vertically.
     computeBlockDirectionPositionsForLine(lineBox, bidiRuns.firstRun(), textBoxDataMap, verticalPositionCache);
     
-#if ENABLE(SVG)
     // SVG text layout code computes vertical & horizontal positions on its own.
     // Note that we still need to execute computeVerticalPositionsForLine() as
     // it calls InlineTextBox::positionLineBox(), which tracks whether the box
     // contains reversed text or not. If we wouldn't do that editing and thus
     // text selection in RTL boxes would not work as expected.
     if (isSVGRootInlineBox) {
-        ASSERT(isSVGText());
-        static_cast<SVGRootInlineBox*>(lineBox)->computePerCharacterLayoutInformation();
+        ASSERT_WITH_SECURITY_IMPLICATION(isSVGText());
+        downcast<SVGRootInlineBox>(*lineBox).computePerCharacterLayoutInformation();
     }
-#endif
     
     // Compute our overflow now.
     lineBox->computeOverflow(lineBox->lineTop(), lineBox->lineBottom(), textBoxDataMap);
     
-#if PLATFORM(MAC)
-    // Highlight acts as an overflow inflation.
-    if (style()->highlight() != nullAtom)
-        lineBox->addHighlightOverflow();
-#endif
     return lineBox;
 }
 
-// Like LayoutState for layout(), LineLayoutState keeps track of global information
-// during an entire linebox tree layout pass (aka layoutInlineChildren).
-class LineLayoutState {
-public:
-    LineLayoutState(bool fullLayout, LayoutUnit& repaintLogicalTop, LayoutUnit& repaintLogicalBottom, RenderFlowThread* flowThread)
-        : m_lastFloat(0)
-        , m_endLine(0)
-        , m_floatIndex(0)
-        , m_endLineLogicalTop(0)
-        , m_endLineMatched(false)
-        , m_checkForFloatsFromLastLine(false)
-        , m_isFullLayout(fullLayout)
-        , m_repaintLogicalTop(repaintLogicalTop)
-        , m_repaintLogicalBottom(repaintLogicalBottom)
-        , m_adjustedLogicalLineTop(0)
-        , m_usesRepaintBounds(false)
-        , m_flowThread(flowThread)
-    { }
-
-    void markForFullLayout() { m_isFullLayout = true; }
-    bool isFullLayout() const { return m_isFullLayout; }
-
-    bool usesRepaintBounds() const { return m_usesRepaintBounds; }
-
-    void setRepaintRange(LayoutUnit logicalHeight)
-    { 
-        m_usesRepaintBounds = true;
-        m_repaintLogicalTop = m_repaintLogicalBottom = logicalHeight; 
-    }
-    
-    void updateRepaintRangeFromBox(RootInlineBox* box, LayoutUnit paginationDelta = 0)
-    {
-        m_usesRepaintBounds = true;
-        m_repaintLogicalTop = min(m_repaintLogicalTop, box->logicalTopVisualOverflow() + min<LayoutUnit>(paginationDelta, 0));
-        m_repaintLogicalBottom = max(m_repaintLogicalBottom, box->logicalBottomVisualOverflow() + max<LayoutUnit>(paginationDelta, 0));
-    }
-    
-    bool endLineMatched() const { return m_endLineMatched; }
-    void setEndLineMatched(bool endLineMatched) { m_endLineMatched = endLineMatched; }
-
-    bool checkForFloatsFromLastLine() const { return m_checkForFloatsFromLastLine; }
-    void setCheckForFloatsFromLastLine(bool check) { m_checkForFloatsFromLastLine = check; }
-
-    LineInfo& lineInfo() { return m_lineInfo; }
-    const LineInfo& lineInfo() const { return m_lineInfo; }
-
-    LayoutUnit endLineLogicalTop() const { return m_endLineLogicalTop; }
-    void setEndLineLogicalTop(LayoutUnit logicalTop) { m_endLineLogicalTop = logicalTop; }
-
-    RootInlineBox* endLine() const { return m_endLine; }
-    void setEndLine(RootInlineBox* line) { m_endLine = line; }
-
-    RenderBlock::FloatingObject* lastFloat() const { return m_lastFloat; }
-    void setLastFloat(RenderBlock::FloatingObject* lastFloat) { m_lastFloat = lastFloat; }
-
-    Vector<RenderBlock::FloatWithRect>& floats() { return m_floats; }
-    
-    unsigned floatIndex() const { return m_floatIndex; }
-    void setFloatIndex(unsigned floatIndex) { m_floatIndex = floatIndex; }
-    
-    LayoutUnit adjustedLogicalLineTop() const { return m_adjustedLogicalLineTop; }
-    void setAdjustedLogicalLineTop(LayoutUnit value) { m_adjustedLogicalLineTop = value; }
-
-    RenderFlowThread* flowThread() const { return m_flowThread; }
-    void setFlowThread(RenderFlowThread* thread) { m_flowThread = thread; }
-
-private:
-    Vector<RenderBlock::FloatWithRect> m_floats;
-    RenderBlock::FloatingObject* m_lastFloat;
-    RootInlineBox* m_endLine;
-    LineInfo m_lineInfo;
-    unsigned m_floatIndex;
-    LayoutUnit m_endLineLogicalTop;
-    bool m_endLineMatched;
-    bool m_checkForFloatsFromLastLine;
-    
-    bool m_isFullLayout;
-
-    // FIXME: Should this be a range object instead of two ints?
-    LayoutUnit& m_repaintLogicalTop;
-    LayoutUnit& m_repaintLogicalBottom;
-
-    LayoutUnit m_adjustedLogicalLineTop;
-
-    bool m_usesRepaintBounds;
-    
-    RenderFlowThread* m_flowThread;
-};
-
-static void deleteLineRange(LineLayoutState& layoutState, RenderArena* arena, RootInlineBox* startLine, RootInlineBox* stopLine = 0)
+static void deleteLineRange(LineLayoutState& layoutState, RootInlineBox* startLine, RootInlineBox* stopLine = 0)
 {
     RootInlineBox* boxToDelete = startLine;
     while (boxToDelete && boxToDelete != stopLine) {
         layoutState.updateRepaintRangeFromBox(boxToDelete);
-        // Note: deleteLineRange(renderArena(), firstRootBox()) is not identical to deleteLineBoxTree().
+        // Note: deleteLineRange(firstRootBox()) is not identical to deleteLineBoxTree().
         // deleteLineBoxTree uses nextLineBox() instead of nextRootBox() when traversing.
         RootInlineBox* next = boxToDelete->nextRootBox();
-        boxToDelete->deleteLine(arena);
+        boxToDelete->deleteLine();
         boxToDelete = next;
     }
 }
 
-void RenderBlock::layoutRunsAndFloats(LineLayoutState& layoutState, bool hasInlineChild)
+void RenderBlockFlow::layoutRunsAndFloats(LineLayoutState& layoutState, bool hasInlineChild)
 {
     // We want to skip ahead to the first dirty line
     InlineBidiResolver resolver;
     RootInlineBox* startLine = determineStartPosition(layoutState, resolver);
+    
+    if (startLine)
+        marginCollapseLinesFromStart(layoutState, startLine);
 
     unsigned consecutiveHyphenatedLines = 0;
     if (startLine) {
@@ -1568,19 +1204,18 @@ void RenderBlock::layoutRunsAndFloats(LineLayoutState& layoutState, bool hasInli
     // determineStartPosition can change the fullLayout flag we have to do this here. Failure to call
     // determineStartPosition first will break fast/repaint/line-flow-with-floats-9.html.
     if (layoutState.isFullLayout() && hasInlineChild && !selfNeedsLayout()) {
-        setNeedsLayout(true, MarkOnlyThis); // Mark as needing a full layout to force us to repaint.
-        RenderView* v = view();
-        if (v && !v->doingFullRepaint() && hasLayer()) {
+        setNeedsLayout(MarkOnlyThis); // Mark as needing a full layout to force us to repaint.
+        if (!view().doingFullRepaint() && hasLayer()) {
             // Because we waited until we were already inside layout to discover
             // that the block really needed a full layout, we missed our chance to repaint the layer
             // before layout started.  Luckily the layer has cached the repaint rect for its original
             // position and size, and so we can use that to make a repaint happen now.
-            repaintUsingContainer(containerForRepaint(), pixelSnappedIntRect(layer()->repaintRect()));
+            repaintUsingContainer(containerForRepaint(), layer()->repaintRect());
         }
     }
 
     if (containsFloats())
-        layoutState.setLastFloat(m_floatingObjects->set().last());
+        layoutState.setLastFloat(m_floatingObjects->set().last().get());
 
     // We also find the first clean line and extract these lines.  We will add them back
     // if we determine that we're able to synchronize after handling all our dirty lines.
@@ -1592,7 +1227,7 @@ void RenderBlock::layoutRunsAndFloats(LineLayoutState& layoutState, bool hasInli
     if (startLine) {
         if (!layoutState.usesRepaintBounds())
             layoutState.setRepaintRange(logicalHeight());
-        deleteLineRange(layoutState, renderArena(), startLine);
+        deleteLineRange(layoutState, startLine);
     }
 
     if (!layoutState.isFullLayout() && lastRootBox() && lastRootBox()->endsWithBreak()) {
@@ -1600,13 +1235,13 @@ void RenderBlock::layoutRunsAndFloats(LineLayoutState& layoutState, bool hasInli
         // adjust the height accordingly.
         // A line break can be either the first or the last object on a line, depending on its direction.
         if (InlineBox* lastLeafChild = lastRootBox()->lastLeafChild()) {
-            RenderObject* lastObject = lastLeafChild->renderer();
+            RenderObject* lastObject = &lastLeafChild->renderer();
             if (!lastObject->isBR())
-                lastObject = lastRootBox()->firstLeafChild()->renderer();
+                lastObject = &lastRootBox()->firstLeafChild()->renderer();
             if (lastObject->isBR()) {
-                EClear clear = lastObject->style()->clear();
+                EClear clear = lastObject->style().clear();
                 if (clear != CNONE)
-                    newLine(clear);
+                    clearFloats(clear);
             }
         }
     }
@@ -1616,18 +1251,8 @@ void RenderBlock::layoutRunsAndFloats(LineLayoutState& layoutState, bool hasInli
     repaintDirtyFloats(layoutState.floats());
 }
 
-RenderBlock::RenderTextInfo::RenderTextInfo()
-    : m_text(0)
-    , m_font(0)
-{
-}
-
-RenderBlock::RenderTextInfo::~RenderTextInfo()
-{
-}
-
 // Before restarting the layout loop with a new logicalHeight, remove all floats that were added and reset the resolver.
-inline const InlineIterator& RenderBlock::restartLayoutRunsAndFloatsInRange(LayoutUnit oldLogicalHeight, LayoutUnit newLogicalHeight,  FloatingObject* lastFloatFromPreviousLine, InlineBidiResolver& resolver,  const InlineIterator& oldEnd)
+inline const InlineIterator& RenderBlockFlow::restartLayoutRunsAndFloatsInRange(LayoutUnit oldLogicalHeight, LayoutUnit newLogicalHeight,  FloatingObject* lastFloatFromPreviousLine, InlineBidiResolver& resolver,  const InlineIterator& oldEnd)
 {
     removeFloatingObjectsBelow(lastFloatFromPreviousLine, oldLogicalHeight);
     setLogicalHeight(newLogicalHeight);
@@ -1635,189 +1260,17 @@ inline const InlineIterator& RenderBlock::restartLayoutRunsAndFloatsInRange(Layo
     return oldEnd;
 }
 
-#if ENABLE(CSS_SHAPES)
-static inline float firstPositiveWidth(const WordMeasurements& wordMeasurements)
-{
-    for (size_t i = 0; i < wordMeasurements.size(); ++i) {
-        if (wordMeasurements[i].width > 0)
-            return wordMeasurements[i].width;
-    }
-    return 0;
-}
-
-static inline LayoutUnit adjustLogicalLineTop(ShapeInsideInfo* shapeInsideInfo, InlineIterator start, InlineIterator end, const WordMeasurements& wordMeasurements)
-{
-    if (!shapeInsideInfo || end != start)
-        return 0;
-
-    float minWidth = firstPositiveWidth(wordMeasurements);
-    ASSERT(minWidth || wordMeasurements.isEmpty());
-    if (minWidth > 0 && shapeInsideInfo->adjustLogicalLineTop(minWidth))
-        return shapeInsideInfo->logicalLineTop();
-
-    return shapeInsideInfo->shapeLogicalBottom();
-}
-
-static inline void pushShapeContentOverflowBelowTheContentBox(RenderBlock* block, ShapeInsideInfo* shapeInsideInfo, LayoutUnit lineTop, LayoutUnit lineHeight)
-{
-    ASSERT(shapeInsideInfo);
-
-    LayoutUnit logicalLineBottom = lineTop + lineHeight;
-    LayoutUnit shapeLogicalBottom = shapeInsideInfo->shapeLogicalBottom();
-    LayoutUnit shapeContainingBlockHeight = shapeInsideInfo->shapeContainingBlockHeight();
-
-    bool isOverflowPositionedAlready = (shapeContainingBlockHeight - shapeInsideInfo->owner()->borderAndPaddingAfter() + lineHeight) <= lineTop;
-
-    // If the last line overlaps with the shape, we don't need the segments anymore
-    if (lineTop < shapeLogicalBottom && shapeLogicalBottom < logicalLineBottom)
-        shapeInsideInfo->clearSegments();
-
-    if (logicalLineBottom <= shapeLogicalBottom || !shapeContainingBlockHeight || isOverflowPositionedAlready)
-        return;
-
-    LayoutUnit newLogicalHeight = block->logicalHeight() + (shapeContainingBlockHeight - (lineTop + shapeInsideInfo->owner()->borderAndPaddingAfter()));
-    block->setLogicalHeight(newLogicalHeight);
-}
-
-void RenderBlock::updateShapeAndSegmentsForCurrentLine(ShapeInsideInfo*& shapeInsideInfo, LayoutUnit& absoluteLogicalTop, LineLayoutState& layoutState)
-{
-    if (layoutState.flowThread())
-        return updateShapeAndSegmentsForCurrentLineInFlowThread(shapeInsideInfo, layoutState);
-
-    if (!shapeInsideInfo)
-        return;
-
-    LayoutUnit lineTop = logicalHeight() + absoluteLogicalTop;
-    LayoutUnit lineHeight = this->lineHeight(layoutState.lineInfo().isFirstLine(), isHorizontalWritingMode() ? HorizontalLine : VerticalLine, PositionOfInteriorLineBoxes);
-
-    // FIXME: Bug 95361: It is possible for a line to grow beyond lineHeight, in which case these segments may be incorrect.
-    shapeInsideInfo->computeSegmentsForLine(lineTop, lineHeight);
-
-    pushShapeContentOverflowBelowTheContentBox(this, shapeInsideInfo, lineTop, lineHeight);
-}
-
-void RenderBlock::updateShapeAndSegmentsForCurrentLineInFlowThread(ShapeInsideInfo*& shapeInsideInfo, LineLayoutState& layoutState)
+void RenderBlockFlow::layoutRunsAndFloatsInRange(LineLayoutState& layoutState, InlineBidiResolver& resolver, const InlineIterator& cleanLineStart, const BidiStatus& cleanLineBidiStatus, unsigned consecutiveHyphenatedLines)
 {
-    ASSERT(layoutState.flowThread());
-
-    LayoutUnit lineHeight = this->lineHeight(layoutState.lineInfo().isFirstLine(), isHorizontalWritingMode() ? HorizontalLine : VerticalLine, PositionOfInteriorLineBoxes);
-
-    RenderRegion* currentRegion = regionAtBlockOffset(logicalHeight());
-    if (!currentRegion)
-        return;
-
-    shapeInsideInfo = currentRegion->shapeInsideInfo();
-
-    LayoutUnit logicalLineTopInFlowThread = logicalHeight() + offsetFromLogicalTopOfFirstPage();
-    LayoutUnit logicalLineBottomInFlowThread = logicalLineTopInFlowThread + lineHeight;
-    LayoutUnit logicalRegionTopInFlowThread = currentRegion->logicalTopForFlowThreadContent();
-    LayoutUnit logicalRegionBottomInFlowThread = logicalRegionTopInFlowThread + currentRegion->logicalHeight() - currentRegion->borderAndPaddingBefore() - currentRegion->borderAndPaddingAfter();
-
-    // We only want to deal regions with shapes, so we look up for the next region whether it has a shape
-    if (!shapeInsideInfo && !currentRegion->isLastRegion()) {
-        LayoutUnit deltaToNextRegion = logicalHeight() + logicalRegionBottomInFlowThread - logicalLineTopInFlowThread;
-        RenderRegion* lookupForNextRegion = regionAtBlockOffset(logicalHeight() + deltaToNextRegion);
-        if (!lookupForNextRegion->shapeInsideInfo())
-            return;
-    }
-
-    LayoutUnit shapeBottomInFlowThread = LayoutUnit::max();
-    if (shapeInsideInfo)
-        shapeBottomInFlowThread = shapeInsideInfo->shapeLogicalBottom() + currentRegion->logicalTopForFlowThreadContent();
-
-    // If the line is between two shapes/regions we position the line to the top of the next shape/region
-    RenderRegion* nextRegion = regionAtBlockOffset(logicalHeight() + lineHeight);
-    if ((currentRegion != nextRegion && (logicalLineBottomInFlowThread > logicalRegionBottomInFlowThread)) || (!currentRegion->isLastRegion() && shapeBottomInFlowThread < logicalLineBottomInFlowThread)) {
-        LayoutUnit deltaToNextRegion = logicalRegionBottomInFlowThread - logicalLineTopInFlowThread;
-        nextRegion = regionAtBlockOffset(logicalHeight() + deltaToNextRegion);
-
-        ASSERT(currentRegion != nextRegion);
-
-        shapeInsideInfo = nextRegion->shapeInsideInfo();
-        setLogicalHeight(logicalHeight() + deltaToNextRegion);
-
-        currentRegion = nextRegion;
-
-        logicalLineTopInFlowThread = logicalHeight() + offsetFromLogicalTopOfFirstPage();
-        logicalLineBottomInFlowThread = logicalLineTopInFlowThread + lineHeight;
-        logicalRegionTopInFlowThread = currentRegion->logicalTopForFlowThreadContent();
-        logicalRegionBottomInFlowThread = logicalRegionTopInFlowThread + currentRegion->logicalHeight() - currentRegion->borderAndPaddingBefore() - currentRegion->borderAndPaddingAfter();
-    }
-
-    if (!shapeInsideInfo)
-        return;
-
-    // We position the first line to the top of the shape in the region or to the previously adjusted position in the shape
-    if (logicalLineBottomInFlowThread <= (logicalRegionTopInFlowThread + lineHeight) || (logicalLineTopInFlowThread - logicalRegionTopInFlowThread) < (layoutState.adjustedLogicalLineTop() - currentRegion->borderAndPaddingBefore())) {
-        LayoutUnit shapeTopOffset = layoutState.adjustedLogicalLineTop();
-        if (!shapeTopOffset)
-            shapeTopOffset = shapeInsideInfo->shapeLogicalTop();
-
-        LayoutUnit shapePositionInFlowThread = currentRegion->logicalTopForFlowThreadContent() + shapeTopOffset;
-        LayoutUnit shapeTopLineTopDelta = shapePositionInFlowThread - logicalLineTopInFlowThread - currentRegion->borderAndPaddingBefore();
-
-        setLogicalHeight(logicalHeight() + shapeTopLineTopDelta);
-        logicalLineTopInFlowThread += shapeTopLineTopDelta;
-        layoutState.setAdjustedLogicalLineTop(0);
-    }
-
-    LayoutUnit lineTop = logicalLineTopInFlowThread - currentRegion->logicalTopForFlowThreadContent() + currentRegion->borderAndPaddingBefore();
-    shapeInsideInfo->computeSegmentsForLine(lineTop, lineHeight);
-
-    if (currentRegion->isLastRegion())
-        pushShapeContentOverflowBelowTheContentBox(this, shapeInsideInfo, lineTop, lineHeight);
-}
-
-bool RenderBlock::adjustLogicalLineTopAndLogicalHeightIfNeeded(ShapeInsideInfo* shapeInsideInfo, LayoutUnit absoluteLogicalTop, LineLayoutState& layoutState, InlineBidiResolver& resolver, FloatingObject* lastFloatFromPreviousLine, InlineIterator& end, WordMeasurements& wordMeasurements)
-{
-    LayoutUnit adjustedLogicalLineTop = adjustLogicalLineTop(shapeInsideInfo, resolver.position(), end, wordMeasurements);
-    if (!adjustedLogicalLineTop)
-        return false;
-
-    LayoutUnit newLogicalHeight = adjustedLogicalLineTop - absoluteLogicalTop;
-
-    if (layoutState.flowThread()) {
-        layoutState.setAdjustedLogicalLineTop(adjustedLogicalLineTop);
-        newLogicalHeight = logicalHeight();
-    }
-
-
-    end = restartLayoutRunsAndFloatsInRange(logicalHeight(), newLogicalHeight, lastFloatFromPreviousLine, resolver, end);
-    return true;
-}
-#endif
-
-void RenderBlock::layoutRunsAndFloatsInRange(LineLayoutState& layoutState, InlineBidiResolver& resolver, const InlineIterator& cleanLineStart, const BidiStatus& cleanLineBidiStatus, unsigned consecutiveHyphenatedLines)
-{
-    RenderStyle* styleToUse = style();
-    bool paginated = view()->layoutState() && view()->layoutState()->isPaginated();
+    const RenderStyle& styleToUse = style();
+    bool paginated = view().layoutState() && view().layoutState()->isPaginated();
     LineMidpointState& lineMidpointState = resolver.midpointState();
     InlineIterator end = resolver.position();
     bool checkForEndLineMatch = layoutState.endLine();
     RenderTextInfo renderTextInfo;
     VerticalPositionCache verticalPositionCache;
 
-    LineBreaker lineBreaker(this);
-
-#if ENABLE(CSS_SHAPES)
-    LayoutUnit absoluteLogicalTop;
-    ShapeInsideInfo* shapeInsideInfo = layoutShapeInsideInfo();
-    if (shapeInsideInfo) {
-        ASSERT(shapeInsideInfo->owner() == this || allowsShapeInsideInfoSharing());
-        if (shapeInsideInfo != this->shapeInsideInfo()) {
-            // FIXME Bug 100284: If subsequent LayoutStates are pushed, we will have to add
-            // their offsets from the original shape-inside container.
-            absoluteLogicalTop = logicalTop();
-        }
-        // Begin layout at the logical top of our shape inside.
-        if (logicalHeight() + absoluteLogicalTop < shapeInsideInfo->shapeLogicalTop()) {
-            LayoutUnit logicalHeight = shapeInsideInfo->shapeLogicalTop() - absoluteLogicalTop;
-            if (layoutState.flowThread())
-                logicalHeight -= shapeInsideInfo->owner()->borderAndPaddingBefore();
-            setLogicalHeight(logicalHeight);
-        }
-    }
-#endif
+    LineBreaker lineBreaker(*this);
 
     while (!end.atEnd()) {
         // FIXME: Is this check necessary before the first iteration or can it be moved to the end?
@@ -1825,6 +1278,7 @@ void RenderBlock::layoutRunsAndFloatsInRange(LineLayoutState& layoutState, Inlin
             layoutState.setEndLineMatched(matchedEndLine(layoutState, resolver, cleanLineStart, cleanLineBidiStatus));
             if (layoutState.endLineMatched()) {
                 resolver.setPosition(InlineIterator(resolver.position().root(), 0, 0), 0);
+                layoutState.marginInfo().clearMargin();
                 break;
             }
         }
@@ -1836,14 +1290,12 @@ void RenderBlock::layoutRunsAndFloatsInRange(LineLayoutState& layoutState, Inlin
 
         const InlineIterator oldEnd = end;
         bool isNewUBAParagraph = layoutState.lineInfo().previousLineBrokeCleanly();
-        FloatingObject* lastFloatFromPreviousLine = (containsFloats()) ? m_floatingObjects->set().last() : 0;
+        FloatingObject* lastFloatFromPreviousLine = (containsFloats()) ? m_floatingObjects->set().last().get() : nullptr;
 
-#if ENABLE(CSS_SHAPES)
-        updateShapeAndSegmentsForCurrentLine(shapeInsideInfo, absoluteLogicalTop, layoutState);
-#endif
         WordMeasurements wordMeasurements;
-        end = lineBreaker.nextLineBreak(resolver, layoutState.lineInfo(), renderTextInfo, lastFloatFromPreviousLine, consecutiveHyphenatedLines, wordMeasurements);
-        renderTextInfo.m_lineBreakIterator.resetPriorContext();
+        end = lineBreaker.nextLineBreak(resolver, layoutState.lineInfo(), layoutState, renderTextInfo, lastFloatFromPreviousLine, consecutiveHyphenatedLines, wordMeasurements);
+        cachePriorCharactersIfNeeded(renderTextInfo.lineBreakIterator);
+        renderTextInfo.lineBreakIterator.resetPriorContext();
         if (resolver.position().atEnd()) {
             // FIXME: We shouldn't be creating any runs in nextLineBreak to begin with!
             // Once BidiRunList is separated from BidiResolver this will not be needed.
@@ -1854,30 +1306,26 @@ void RenderBlock::layoutRunsAndFloatsInRange(LineLayoutState& layoutState, Inlin
             break;
         }
 
-#if ENABLE(CSS_SHAPES)
-        if (adjustLogicalLineTopAndLogicalHeightIfNeeded(shapeInsideInfo, absoluteLogicalTop, layoutState, resolver, lastFloatFromPreviousLine, end, wordMeasurements))
-            continue;
-#endif
         ASSERT(end != resolver.position());
 
         // This is a short-cut for empty lines.
         if (layoutState.lineInfo().isEmpty()) {
             if (lastRootBox())
-                lastRootBox()->setLineBreakInfo(end.m_obj, end.m_pos, resolver.status());
+                lastRootBox()->setLineBreakInfo(end.renderer(), end.offset(), resolver.status());
         } else {
-            VisualDirectionOverride override = (styleToUse->rtlOrdering() == VisualOrder ? (styleToUse->direction() == LTR ? VisualLeftToRightOverride : VisualRightToLeftOverride) : NoVisualOverride);
+            VisualDirectionOverride override = (styleToUse.rtlOrdering() == VisualOrder ? (styleToUse.direction() == LTR ? VisualLeftToRightOverride : VisualRightToLeftOverride) : NoVisualOverride);
 
-            if (isNewUBAParagraph && styleToUse->unicodeBidi() == Plaintext && !resolver.context()->parent()) {
-                TextDirection direction = styleToUse->direction();
+            if (isNewUBAParagraph && styleToUse.unicodeBidi() == Plaintext && !resolver.context()->parent()) {
+                TextDirection direction = styleToUse.direction();
                 determineDirectionality(direction, resolver.position());
-                resolver.setStatus(BidiStatus(direction, isOverride(styleToUse->unicodeBidi())));
+                resolver.setStatus(BidiStatus(direction, isOverride(styleToUse.unicodeBidi())));
             }
             // FIXME: This ownership is reversed. We should own the BidiRunList and pass it to createBidiRunsForLine.
             BidiRunList<BidiRun>& bidiRuns = resolver.runs();
-            constructBidiRunsForLine(this, resolver, bidiRuns, end, override, layoutState.lineInfo().previousLineBrokeCleanly());
+            constructBidiRunsForSegment(resolver, bidiRuns, end, override, layoutState.lineInfo().previousLineBrokeCleanly());
             ASSERT(resolver.position() == end);
 
-            BidiRun* trailingSpaceRun = !layoutState.lineInfo().previousLineBrokeCleanly() ? handleTrailingSpaces(bidiRuns, resolver.context()) : 0;
+            BidiRun* trailingSpaceRun = !layoutState.lineInfo().previousLineBrokeCleanly() ? handleTrailingSpaces(bidiRuns, resolver.context()) : nullptr;
 
             if (bidiRuns.runCount() && lineBreaker.lineWasHyphenated()) {
                 bidiRuns.logicallyLastRun()->m_hasHyphen = true;
@@ -1890,76 +1338,109 @@ void RenderBlock::layoutRunsAndFloatsInRange(LineLayoutState& layoutState, Inlin
             // inline flow boxes.
 
             LayoutUnit oldLogicalHeight = logicalHeight();
-            RootInlineBox* lineBox = createLineBoxesFromBidiRuns(bidiRuns, end, layoutState.lineInfo(), verticalPositionCache, trailingSpaceRun, wordMeasurements);
+            RootInlineBox* lineBox = createLineBoxesFromBidiRuns(resolver.status().context->level(), bidiRuns, end, layoutState.lineInfo(), verticalPositionCache, trailingSpaceRun, wordMeasurements);
 
             bidiRuns.deleteRuns();
             resolver.markCurrentRunEmpty(); // FIXME: This can probably be replaced by an ASSERT (or just removed).
 
             if (lineBox) {
-                lineBox->setLineBreakInfo(end.m_obj, end.m_pos, resolver.status());
+                lineBox->setLineBreakInfo(end.renderer(), end.offset(), resolver.status());
                 if (layoutState.usesRepaintBounds())
                     layoutState.updateRepaintRangeFromBox(lineBox);
+                
+                LayoutUnit adjustment = 0;
+                bool overflowsRegion = false;
+                
+                // If our previous line was an anonymous block and we are not an anonymous block,
+                // simulate a margin collapse now so that we get the proper
+                // increased height. We also have to simulate a margin collapse to propagate margins
+                // through to the top of our block.
+                if (!lineBox->hasAnonymousInlineBlock()) {
+                    RootInlineBox* prevRoot = lineBox->prevRootBox();
+                    if (prevRoot && prevRoot->hasAnonymousInlineBlock()) {
+                        LayoutUnit currentLogicalHeight = logicalHeight();
+                        setLogicalHeight(oldLogicalHeight);
+                        collapseMarginsWithChildInfo(nullptr, nullptr, layoutState.marginInfo());
+                        adjustment = logicalHeight() - oldLogicalHeight;
+                        setLogicalHeight(currentLogicalHeight);
+                    }
+                    layoutState.marginInfo().setAtBeforeSideOfBlock(false);
+                }
 
+                if (paginated)
+                    adjustLinePositionForPagination(lineBox, adjustment, overflowsRegion, layoutState.flowThread());
+                if (adjustment) {
+                    IndentTextOrNot shouldIndentText = layoutState.lineInfo().isFirstLine() ? IndentText : DoNotIndentText;
+                    LayoutUnit oldLineWidth = availableLogicalWidthForLine(oldLogicalHeight, shouldIndentText);
+                    lineBox->adjustBlockDirectionPosition(adjustment);
+                    if (layoutState.usesRepaintBounds())
+                        layoutState.updateRepaintRangeFromBox(lineBox);
+
+                    if (availableLogicalWidthForLine(oldLogicalHeight + adjustment, shouldIndentText) != oldLineWidth) {
+                        // We have to delete this line, remove all floats that got added, and let line layout re-run.
+                        lineBox->deleteLine();
+                        end = restartLayoutRunsAndFloatsInRange(oldLogicalHeight, oldLogicalHeight + adjustment, lastFloatFromPreviousLine, resolver, oldEnd);
+                        continue;
+                    }
+
+                    setLogicalHeight(lineBox->lineBottomWithLeading());
+                }
+                    
                 if (paginated) {
-                    LayoutUnit adjustment = 0;
-                    adjustLinePositionForPagination(lineBox, adjustment, layoutState.flowThread());
-                    if (adjustment) {
-                        LayoutUnit oldLineWidth = availableLogicalWidthForLine(oldLogicalHeight, layoutState.lineInfo().isFirstLine());
-                        lineBox->adjustBlockDirectionPosition(adjustment);
-                        if (layoutState.usesRepaintBounds())
-                            layoutState.updateRepaintRangeFromBox(lineBox);
-
-                        if (availableLogicalWidthForLine(oldLogicalHeight + adjustment, layoutState.lineInfo().isFirstLine()) != oldLineWidth) {
-                            // We have to delete this line, remove all floats that got added, and let line layout re-run.
-                            lineBox->deleteLine(renderArena());
-                            end = restartLayoutRunsAndFloatsInRange(oldLogicalHeight, oldLogicalHeight + adjustment, lastFloatFromPreviousLine, resolver, oldEnd);
-                            continue;
+                    if (RenderFlowThread* flowThread = flowThreadContainingBlock()) {
+                        if (flowThread->isRenderNamedFlowThread() && overflowsRegion && hasNextPage(lineBox->lineTop())) {
+                            // Limit the height of this block to the end of the current region because
+                            // it is also fragmented into the next region.
+                            LayoutUnit remainingLogicalHeight = pageRemainingLogicalHeightForOffset(logicalTop(), ExcludePageBoundary);
+                            if (logicalHeight() > remainingLogicalHeight)
+                                setLogicalHeight(remainingLogicalHeight);
                         }
-
-                        setLogicalHeight(lineBox->lineBottomWithLeading());
                     }
 
                     if (layoutState.flowThread())
-                        lineBox->setContainingRegion(regionAtBlockOffset(lineBox->lineTopWithLeading()));
+                        updateRegionForLine(lineBox);
                 }
             }
         }
 
         for (size_t i = 0; i < lineBreaker.positionedObjects().size(); ++i)
-            setStaticPositions(this, lineBreaker.positionedObjects()[i]);
+            setStaticPositions(*this, *lineBreaker.positionedObjects()[i], DoNotIndentText);
 
         if (!layoutState.lineInfo().isEmpty()) {
             layoutState.lineInfo().setFirstLine(false);
-            newLine(lineBreaker.clear());
+            clearFloats(lineBreaker.clear());
         }
 
         if (m_floatingObjects && lastRootBox()) {
             const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-            FloatingObjectSetIterator it = floatingObjectSet.begin();
-            FloatingObjectSetIterator end = floatingObjectSet.end();
+            auto it = floatingObjectSet.begin();
+            auto end = floatingObjectSet.end();
             if (layoutState.lastFloat()) {
-                FloatingObjectSetIterator lastFloatIterator = floatingObjectSet.find(layoutState.lastFloat());
+                auto lastFloatIterator = floatingObjectSet.find<FloatingObject&, FloatingObjectHashTranslator>(*layoutState.lastFloat());
                 ASSERT(lastFloatIterator != end);
                 ++lastFloatIterator;
                 it = lastFloatIterator;
             }
             for (; it != end; ++it) {
-                FloatingObject* f = *it;
+                FloatingObject* f = it->get();
                 appendFloatingObjectToLastLine(f);
-                ASSERT(f->m_renderer == layoutState.floats()[layoutState.floatIndex()].object);
+                ASSERT(&f->renderer() == &layoutState.floats()[layoutState.floatIndex()].object);
                 // If a float's geometry has changed, give up on syncing with clean lines.
                 if (layoutState.floats()[layoutState.floatIndex()].rect != f->frameRect())
                     checkForEndLineMatch = false;
                 layoutState.setFloatIndex(layoutState.floatIndex() + 1);
             }
-            layoutState.setLastFloat(!floatingObjectSet.isEmpty() ? floatingObjectSet.last() : 0);
+            layoutState.setLastFloat(!floatingObjectSet.isEmpty() ? floatingObjectSet.last().get() : nullptr);
         }
 
         lineMidpointState.reset();
         resolver.setPosition(end, numberOfIsolateAncestors(end));
     }
 
-    if (paginated && !style()->hasAutoWidows()) {
+    // In case we already adjusted the line positions during this layout to avoid widows
+    // then we need to ignore the possibility of having a new widows situation.
+    // Otherwise, we risk leaving empty containers which is against the block fragmentation principles.
+    if (paginated && !style().hasAutoWidows() && !didBreakAtLineToAvoidWidow()) {
         // Check the line boxes to make sure we didn't create unacceptable widows.
         // However, we'll prioritize orphans - so nothing we do here should create
         // a new orphan.
@@ -1979,11 +1460,11 @@ void RenderBlock::layoutRunsAndFloatsInRange(LineLayoutState& layoutState, Inlin
         if (!lineBox || !lineBox->isFirstAfterPageBreak() || lineBox == firstLineInBlock)
             return;
 
-        if (numLinesHanging < style()->widows()) {
+        if (numLinesHanging < style().widows()) {
             // We have detected a widow. Now we need to work out how many
             // lines there are on the previous page, and how many we need
             // to steal.
-            int numLinesNeeded = style()->widows() - numLinesHanging;
+            int numLinesNeeded = style().widows() - numLinesHanging;
             RootInlineBox* currentFirstLineOfNewPage = lineBox;
 
             // Count the number of lines in the previous page.
@@ -1999,58 +1480,73 @@ void RenderBlock::layoutRunsAndFloatsInRange(LineLayoutState& layoutState, Inlin
             // This means that setting widows implies we also care about orphans, but given
             // the specification says the initial orphan value is non-zero, this is ok. The
             // author is always free to set orphans explicitly as well.
-            int orphans = style()->hasAutoOrphans() ? style()->initialOrphans() : style()->orphans();
+            int orphans = style().hasAutoOrphans() ? style().initialOrphans() : style().orphans();
             int numLinesAvailable = numLinesInPreviousPage - orphans;
             if (numLinesAvailable <= 0)
                 return;
 
-            int numLinesToTake = min(numLinesAvailable, numLinesNeeded);
+            int numLinesToTake = std::min(numLinesAvailable, numLinesNeeded);
             // Wind back from our first widowed line.
             lineBox = currentFirstLineOfNewPage;
             for (int i = 0; i < numLinesToTake; ++i)
                 lineBox = lineBox->prevRootBox();
 
             // We now want to break at this line. Remember for next layout and trigger relayout.
-            setBreakAtLineToAvoidWidow(lineBox);
+            setBreakAtLineToAvoidWidow(lineCount(lineBox));
             markLinesDirtyInBlockRange(lastRootBox()->lineBottomWithLeading(), lineBox->lineBottomWithLeading(), lineBox);
         }
     }
+    clearDidBreakAtLineToAvoidWidow();
 }
 
-void RenderBlock::linkToEndLineIfNeeded(LineLayoutState& layoutState)
+void RenderBlockFlow::reattachCleanLineFloats(RootInlineBox& cleanLine, LayoutUnit delta, bool isFirstCleanLine)
 {
-    if (layoutState.endLine()) {
+    auto* cleanLineFloats = cleanLine.floatsPtr();
+    if (!cleanLineFloats)
+        return;
+
+    for (auto* floatingBox : *cleanLineFloats) {
+        auto* floatingObject = insertFloatingObject(*floatingBox);
+        if (isFirstCleanLine && floatingObject->originatingLine()) {
+            // Float box does not belong to this line anymore.
+            ASSERT_WITH_SECURITY_IMPLICATION(cleanLine.prevRootBox() == floatingObject->originatingLine());
+            cleanLine.removeFloat(*floatingBox);
+            continue;
+        }
+        ASSERT_WITH_SECURITY_IMPLICATION(!floatingObject->originatingLine());
+        floatingObject->setOriginatingLine(&cleanLine);
+        setLogicalHeight(logicalTopForChild(*floatingBox) - marginBeforeForChild(*floatingBox) + delta);
+        positionNewFloats();
+    }
+}
+
+void RenderBlockFlow::linkToEndLineIfNeeded(LineLayoutState& layoutState)
+{
+    auto* firstCleanLine = layoutState.endLine();
+    if (firstCleanLine) {
         if (layoutState.endLineMatched()) {
-            bool paginated = view()->layoutState() && view()->layoutState()->isPaginated();
+            bool paginated = view().layoutState() && view().layoutState()->isPaginated();
             // Attach all the remaining lines, and then adjust their y-positions as needed.
             LayoutUnit delta = logicalHeight() - layoutState.endLineLogicalTop();
-            for (RootInlineBox* line = layoutState.endLine(); line; line = line->nextRootBox()) {
+            for (auto* line = firstCleanLine; line; line = line->nextRootBox()) {
                 line->attachLine();
                 if (paginated) {
                     delta -= line->paginationStrut();
-                    adjustLinePositionForPagination(line, delta, layoutState.flowThread());
+                    bool overflowsRegion;
+                    adjustLinePositionForPagination(line, delta, overflowsRegion, layoutState.flowThread());
                 }
                 if (delta) {
                     layoutState.updateRepaintRangeFromBox(line, delta);
                     line->adjustBlockDirectionPosition(delta);
                 }
                 if (layoutState.flowThread())
-                    line->setContainingRegion(regionAtBlockOffset(line->lineTopWithLeading()));
-                if (Vector<RenderBox*>* cleanLineFloats = line->floatsPtr()) {
-                    Vector<RenderBox*>::iterator end = cleanLineFloats->end();
-                    for (Vector<RenderBox*>::iterator f = cleanLineFloats->begin(); f != end; ++f) {
-                        FloatingObject* floatingObject = insertFloatingObject(*f);
-                        ASSERT(!floatingObject->m_originatingLine);
-                        floatingObject->m_originatingLine = line;
-                        setLogicalHeight(logicalTopForChild(*f) - marginBeforeForChild(*f) + delta);
-                        positionNewFloats();
-                    }
-                }
+                    updateRegionForLine(line);
+                reattachCleanLineFloats(*line, delta, line == firstCleanLine);
             }
             setLogicalHeight(lastRootBox()->lineBottomWithLeading());
         } else {
             // Delete all the remaining lines.
-            deleteLineRange(layoutState, renderArena(), layoutState.endLine());
+            deleteLineRange(layoutState, layoutState.endLine());
         }
     }
     
@@ -2061,8 +1557,9 @@ void RenderBlock::linkToEndLineIfNeeded(LineLayoutState& layoutState)
         if (layoutState.checkForFloatsFromLastLine()) {
             LayoutUnit bottomVisualOverflow = lastRootBox()->logicalBottomVisualOverflow();
             LayoutUnit bottomLayoutOverflow = lastRootBox()->logicalBottomLayoutOverflow();
-            TrailingFloatsRootInlineBox* trailingFloatsLineBox = new (renderArena()) TrailingFloatsRootInlineBox(this);
-            m_lineBoxes.appendLineBox(trailingFloatsLineBox);
+            auto newLineBox = std::make_unique<TrailingFloatsRootInlineBox>(*this);
+            auto trailingFloatsLineBox = newLineBox.get();
+            m_lineBoxes.appendLineBox(WTFMove(newLineBox));
             trailingFloatsLineBox->setConstructed();
             GlyphOverflowAndFallbackFontsMap textBoxDataMap;
             VerticalPositionCache verticalPositionCache;
@@ -2074,25 +1571,25 @@ void RenderBlock::linkToEndLineIfNeeded(LineLayoutState& layoutState)
             LayoutRect logicalVisualOverflow(0, blockLogicalHeight, 1, bottomVisualOverflow - blockLogicalHeight);
             trailingFloatsLineBox->setOverflowFromLogicalRects(logicalLayoutOverflow, logicalVisualOverflow, trailingFloatsLineBox->lineTop(), trailingFloatsLineBox->lineBottom());
             if (layoutState.flowThread())
-                trailingFloatsLineBox->setContainingRegion(regionAtBlockOffset(trailingFloatsLineBox->lineTopWithLeading()));
+                updateRegionForLine(trailingFloatsLineBox);
         }
 
         const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-        FloatingObjectSetIterator it = floatingObjectSet.begin();
-        FloatingObjectSetIterator end = floatingObjectSet.end();
+        auto it = floatingObjectSet.begin();
+        auto end = floatingObjectSet.end();
         if (layoutState.lastFloat()) {
-            FloatingObjectSetIterator lastFloatIterator = floatingObjectSet.find(layoutState.lastFloat());
+            auto lastFloatIterator = floatingObjectSet.find<FloatingObject&, FloatingObjectHashTranslator>(*layoutState.lastFloat());
             ASSERT(lastFloatIterator != end);
             ++lastFloatIterator;
             it = lastFloatIterator;
         }
         for (; it != end; ++it)
-            appendFloatingObjectToLastLine(*it);
-        layoutState.setLastFloat(!floatingObjectSet.isEmpty() ? floatingObjectSet.last() : 0);
+            appendFloatingObjectToLastLine(it->get());
+        layoutState.setLastFloat(!floatingObjectSet.isEmpty() ? floatingObjectSet.last().get() : nullptr);
     }
 }
 
-void RenderBlock::repaintDirtyFloats(Vector<FloatWithRect>& floats)
+void RenderBlockFlow::repaintDirtyFloats(Vector<FloatWithRect>& floats)
 {
     size_t floatCount = floats.size();
     // Floats that did not have layout did not repaint when we laid them out. They would have
@@ -2100,31 +1597,33 @@ void RenderBlock::repaintDirtyFloats(Vector<FloatWithRect>& floats)
     // painted.
     for (size_t i = 0; i < floatCount; ++i) {
         if (!floats[i].everHadLayout) {
-            RenderBox* f = floats[i].object;
-            if (!f->x() && !f->y() && f->checkForRepaintDuringLayout())
-                f->repaint();
+            RenderBox& box = floats[i].object;
+            if (!box.x() && !box.y() && box.checkForRepaintDuringLayout())
+                box.repaint();
         }
     }
 }
 
-void RenderBlock::layoutInlineChildren(bool relayoutChildren, LayoutUnit& repaintLogicalTop, LayoutUnit& repaintLogicalBottom)
+void RenderBlockFlow::layoutLineBoxes(bool relayoutChildren, LayoutUnit& repaintLogicalTop, LayoutUnit& repaintLogicalBottom)
 {
+    ASSERT(!m_simpleLineLayout);
+
     setLogicalHeight(borderAndPaddingBefore());
     
     // Lay out our hypothetical grid line as though it occurs at the top of the block.
-    if (view()->layoutState() && view()->layoutState()->lineGrid() == this)
+    if (view().layoutState() && view().layoutState()->lineGrid() == this)
         layoutLineGridBox();
 
     RenderFlowThread* flowThread = flowThreadContainingBlock();
-    bool clearLinesForPagination = firstLineBox() && flowThread && !flowThread->hasRegions();
+    bool clearLinesForPagination = firstRootBox() && flowThread && !flowThread->hasRegions();
 
     // Figure out if we should clear out our line boxes.
     // FIXME: Handle resize eventually!
-    bool isFullLayout = !firstLineBox() || selfNeedsLayout() || relayoutChildren || clearLinesForPagination;
-    LineLayoutState layoutState(isFullLayout, repaintLogicalTop, repaintLogicalBottom, flowThread);
+    bool isFullLayout = !firstRootBox() || selfNeedsLayout() || relayoutChildren || clearLinesForPagination;
+    LineLayoutState layoutState(*this, isFullLayout, repaintLogicalTop, repaintLogicalBottom, flowThread);
 
     if (isFullLayout)
-        lineBoxes()->deleteLineBoxes(renderArena());
+        lineBoxes().deleteLineBoxes();
 
     // Text truncation kicks in in two cases:
     //     1) If your overflow isn't visible and your text-overflow-mode isn't clip.
@@ -2132,8 +1631,8 @@ void RenderBlock::layoutInlineChildren(bool relayoutChildren, LayoutUnit& repain
     // FIXME: CSS3 says that descendants that are clipped must also know how to truncate.  This is insanely
     // difficult to figure out in general (especially in the middle of doing layout), so we only handle the
     // simple case of an anonymous block truncating when it's parent is clipped.
-    bool hasTextOverflow = (style()->textOverflow() && hasOverflowClip())
-        || (isAnonymousBlock() && parent() && parent()->isRenderBlock() && parent()->style()->textOverflow() && parent()->hasOverflowClip());
+    bool hasTextOverflow = (style().textOverflow() && hasOverflowClip())
+        || (isAnonymousBlock() && parent() && parent()->isRenderBlock() && parent()->style().textOverflow() && parent()->hasOverflowClip());
 
     // Walk all the lines and delete our ellipsis line boxes if they exist.
     if (hasTextOverflow)
@@ -2147,39 +1646,42 @@ void RenderBlock::layoutInlineChildren(bool relayoutChildren, LayoutUnit& repain
         // elements at the same time.
         bool hasInlineChild = false;
         Vector<RenderBox*> replacedChildren;
-        for (InlineWalker walker(this); !walker.atEnd(); walker.advance()) {
-            RenderObject* o = walker.current();
-            if (!hasInlineChild && o->isInline())
+        for (InlineWalker walker(*this); !walker.atEnd(); walker.advance()) {
+            RenderObject& o = *walker.current();
+
+            if (!hasInlineChild && o.isInline())
                 hasInlineChild = true;
 
-            if (o->isReplaced() || o->isFloating() || o->isOutOfFlowPositioned()) {
-                RenderBox* box = toRenderBox(o);
+            if (o.isReplaced() || o.isFloating() || o.isOutOfFlowPositioned()) {
+                RenderBox& box = downcast<RenderBox>(o);
 
-                if (relayoutChildren || box->hasRelativeDimensions())
-                    o->setChildNeedsLayout(true, MarkOnlyThis);
+                if (relayoutChildren || box.hasRelativeDimensions())
+                    box.setChildNeedsLayout(MarkOnlyThis);
 
                 // If relayoutChildren is set and the child has percentage padding or an embedded content box, we also need to invalidate the childs pref widths.
-                if (relayoutChildren && box->needsPreferredWidthsRecalculation())
-                    o->setPreferredLogicalWidthsDirty(true, MarkOnlyThis);
+                if (relayoutChildren && box.needsPreferredWidthsRecalculation())
+                    box.setPreferredLogicalWidthsDirty(true, MarkOnlyThis);
 
-                if (o->isOutOfFlowPositioned())
-                    o->containingBlock()->insertPositionedObject(box);
-                else if (o->isFloating())
+                if (box.isOutOfFlowPositioned())
+                    box.containingBlock()->insertPositionedObject(box);
+                else if (box.isFloating())
                     layoutState.floats().append(FloatWithRect(box));
-                else if (isFullLayout || o->needsLayout()) {
+                else if (isFullLayout || box.needsLayout()) {
                     // Replaced element.
-                    box->dirtyLineBoxes(isFullLayout);
-                    if (isFullLayout)
-                        replacedChildren.append(box);
-                    else
-                        o->layoutIfNeeded();
+                    box.dirtyLineBoxes(isFullLayout);
+                    if (!o.isAnonymousInlineBlock()) {
+                        if (isFullLayout)
+                            replacedChildren.append(&box);
+                        else
+                            box.layoutIfNeeded();
+                    }
                 }
-            } else if (o->isText() || (o->isRenderInline() && !walker.atEndOfInline())) {
-                if (!o->isText())
-                    toRenderInline(o)->updateAlwaysCreateLineBoxes(layoutState.isFullLayout());
-                if (layoutState.isFullLayout() || o->selfNeedsLayout())
+            } else if (o.isTextOrLineBreak() || (is<RenderInline>(o) && !walker.atEndOfInline())) {
+                if (is<RenderInline>(o))
+                    downcast<RenderInline>(o).updateAlwaysCreateLineBoxes(layoutState.isFullLayout());
+                if (layoutState.isFullLayout() || o.selfNeedsLayout())
                     dirtyLineBoxesForRenderer(o, layoutState.isFullLayout());
-                o->setNeedsLayout(false);
+                o.clearNeedsLayout();
             }
         }
 
@@ -2192,17 +1694,25 @@ void RenderBlock::layoutInlineChildren(bool relayoutChildren, LayoutUnit& repain
     // Expand the last line to accommodate Ruby and emphasis marks.
     int lastLineAnnotationsAdjustment = 0;
     if (lastRootBox()) {
-        LayoutUnit lowestAllowedPosition = max(lastRootBox()->lineBottom(), logicalHeight() + paddingAfter());
-        if (!style()->isFlippedLinesWritingMode())
+        LayoutUnit lowestAllowedPosition = std::max(lastRootBox()->lineBottom(), logicalHeight() + paddingAfter());
+        if (!style().isFlippedLinesWritingMode())
             lastLineAnnotationsAdjustment = lastRootBox()->computeUnderAnnotationAdjustment(lowestAllowedPosition);
         else
             lastLineAnnotationsAdjustment = lastRootBox()->computeOverAnnotationAdjustment(lowestAllowedPosition);
     }
+    
+    // Now do the handling of the bottom of the block, adding in our bottom border/padding and
+    // determining the correct collapsed bottom margin information. This collapse is only necessary
+    // if our last child was an anonymous inline block that might need to propagate margin information out to
+    // us.
+    LayoutUnit beforeEdge = borderAndPaddingBefore();
+    LayoutUnit afterEdge = borderAndPaddingAfter() + scrollbarLogicalHeight() + lastLineAnnotationsAdjustment;
+    if (lastRootBox() && lastRootBox()->hasAnonymousInlineBlock())
+        handleAfterSideOfBlock(beforeEdge, afterEdge, layoutState.marginInfo());
+    else
+        setLogicalHeight(logicalHeight() + afterEdge);
 
-    // Now add in the bottom border/padding.
-    setLogicalHeight(logicalHeight() + lastLineAnnotationsAdjustment + borderAndPaddingAfter() + scrollbarLogicalHeight());
-
-    if (!firstLineBox() && hasLineIfEmpty())
+    if (!firstRootBox() && hasLineIfEmpty())
         setLogicalHeight(logicalHeight() + lineHeight(true, isHorizontalWritingMode() ? HorizontalLine : VerticalLine, PositionOfInteriorLineBoxes));
 
     // See if we have any lines that spill out of our block.  If we do, then we will possibly need to
@@ -2211,28 +1721,33 @@ void RenderBlock::layoutInlineChildren(bool relayoutChildren, LayoutUnit& repain
         checkLinesForTextOverflow();
 }
 
-void RenderBlock::checkFloatsInCleanLine(RootInlineBox* line, Vector<FloatWithRect>& floats, size_t& floatIndex, bool& encounteredNewFloat, bool& dirtiedByFloat)
+void RenderBlockFlow::checkFloatsInCleanLine(RootInlineBox* line, Vector<FloatWithRect>& floats, size_t& floatIndex, bool& encounteredNewFloat, bool& dirtiedByFloat)
 {
     Vector<RenderBox*>* cleanLineFloats = line->floatsPtr();
     if (!cleanLineFloats)
         return;
+    
+    if (!floats.size()) {
+        encounteredNewFloat = true;
+        return;
+    }
 
-    Vector<RenderBox*>::iterator end = cleanLineFloats->end();
-    for (Vector<RenderBox*>::iterator it = cleanLineFloats->begin(); it != end; ++it) {
+    for (auto it = cleanLineFloats->begin(), end = cleanLineFloats->end(); it != end; ++it) {
         RenderBox* floatingBox = *it;
         floatingBox->layoutIfNeeded();
-        LayoutSize newSize(floatingBox->width() + floatingBox->marginWidth(), floatingBox->height() + floatingBox->marginHeight());
+        LayoutSize newSize(floatingBox->width() + floatingBox->horizontalMarginExtent(), floatingBox->height() + floatingBox->verticalMarginExtent());
         ASSERT_WITH_SECURITY_IMPLICATION(floatIndex < floats.size());
-        if (floats[floatIndex].object != floatingBox) {
+        if (&floats[floatIndex].object != floatingBox) {
             encounteredNewFloat = true;
             return;
         }
-
-        if (floats[floatIndex].rect.size() != newSize) {
+    
+        // We have to reset the cap-height alignment done by the first-letter floats when initial-letter is set, so just always treat first-letter floats
+        // as dirty.
+        if (floats[floatIndex].rect.size() != newSize || (floatingBox->style().styleType() == FIRST_LETTER && floatingBox->style().initialLetterDrop() > 0)) {
             LayoutUnit floatTop = isHorizontalWritingMode() ? floats[floatIndex].rect.y() : floats[floatIndex].rect.x();
-            LayoutUnit floatHeight = isHorizontalWritingMode() ? max(floats[floatIndex].rect.height(), newSize.height())
-                                                                 : max(floats[floatIndex].rect.width(), newSize.width());
-            floatHeight = min(floatHeight, LayoutUnit::max() - floatTop);
+            LayoutUnit floatHeight = isHorizontalWritingMode() ? std::max(floats[floatIndex].rect.height(), newSize.height()) : std::max(floats[floatIndex].rect.width(), newSize.width());
+            floatHeight = std::min(floatHeight, LayoutUnit::max() - floatTop);
             line->markDirty();
             markLinesDirtyInBlockRange(line->lineBottomWithLeading(), floatTop + floatHeight, line);
             floats[floatIndex].rect.setSize(newSize);
@@ -2242,7 +1757,7 @@ void RenderBlock::checkFloatsInCleanLine(RootInlineBox* line, Vector<FloatWithRe
     }
 }
 
-RootInlineBox* RenderBlock::determineStartPosition(LineLayoutState& layoutState, InlineBidiResolver& resolver)
+RootInlineBox* RenderBlockFlow::determineStartPosition(LineLayoutState& layoutState, InlineBidiResolver& resolver)
 {
     RootInlineBox* curr = 0;
     RootInlineBox* last = 0;
@@ -2251,7 +1766,7 @@ RootInlineBox* RenderBlock::determineStartPosition(LineLayoutState& layoutState,
     bool dirtiedByFloat = false;
     if (!layoutState.isFullLayout()) {
         // Paginate all of the clean lines.
-        bool paginated = view()->layoutState() && view()->layoutState()->isPaginated();
+        bool paginated = view().layoutState() && view().layoutState()->isPaginated();
         LayoutUnit paginationDelta = 0;
         size_t floatIndex = 0;
         for (curr = firstRootBox(); curr && !curr->isDirty(); curr = curr->nextRootBox()) {
@@ -2261,7 +1776,8 @@ RootInlineBox* RenderBlock::determineStartPosition(LineLayoutState& layoutState,
                     break;
                 }
                 paginationDelta -= curr->paginationStrut();
-                adjustLinePositionForPagination(curr, paginationDelta, layoutState.flowThread());
+                bool overflowsRegion;
+                adjustLinePositionForPagination(curr, paginationDelta, overflowsRegion, layoutState.flowThread());
                 if (paginationDelta) {
                     if (containsFloats() || !layoutState.floats().isEmpty()) {
                         // FIXME: Do better eventually.  For now if we ever shift because of pagination and floats are present just go to a full layout.
@@ -2273,7 +1789,7 @@ RootInlineBox* RenderBlock::determineStartPosition(LineLayoutState& layoutState,
                     curr->adjustBlockDirectionPosition(paginationDelta);
                 }
                 if (layoutState.flowThread())
-                    curr->setContainingRegion(regionAtBlockOffset(curr->lineTopWithLeading()));
+                    updateRegionForLine(curr);
             }
 
             // If a new float has been inserted before this line or before its last known float, just do a full layout.
@@ -2291,27 +1807,22 @@ RootInlineBox* RenderBlock::determineStartPosition(LineLayoutState& layoutState,
     }
 
     if (layoutState.isFullLayout()) {
-        m_lineBoxes.deleteLineBoxTree(renderArena());
+        m_lineBoxes.deleteLineBoxTree();
         curr = 0;
 
-        ASSERT(!firstLineBox() && !lastLineBox());
+        ASSERT(!firstRootBox() && !lastRootBox());
     } else {
         if (curr) {
             // We have a dirty line.
             if (RootInlineBox* prevRootBox = curr->prevRootBox()) {
                 // We have a previous line.
-                if (!dirtiedByFloat && (!prevRootBox->endsWithBreak() || !prevRootBox->lineBreakObj() || (prevRootBox->lineBreakObj()->isText() && prevRootBox->lineBreakPos() >= toRenderText(prevRootBox->lineBreakObj())->textLength())))
+                if (!dirtiedByFloat && !curr->hasAnonymousInlineBlock() && (!prevRootBox->endsWithBreak() || !prevRootBox->lineBreakObj() || (is<RenderText>(*prevRootBox->lineBreakObj()) && prevRootBox->lineBreakPos() >= downcast<RenderText>(*prevRootBox->lineBreakObj()).textLength()))) {
                     // The previous line didn't break cleanly or broke at a newline
                     // that has been deleted, so treat it as dirty too.
                     curr = prevRootBox;
+                }
             }
-        } else {
-            // No dirty lines were found.
-            // If the last line didn't break cleanly, treat it as dirty.
-            if (lastRootBox() && !lastRootBox()->endsWithBreak())
-                curr = lastRootBox();
         }
-
         // If we have no dirty lines, then last is just the last root box.
         last = curr ? curr->prevRootBox() : lastRootBox();
     }
@@ -2323,14 +1834,14 @@ RootInlineBox* RenderBlock::determineStartPosition(LineLayoutState& layoutState,
         RootInlineBox* line = firstRootBox();
         while (line != curr) {
             if (Vector<RenderBox*>* cleanLineFloats = line->floatsPtr()) {
-                Vector<RenderBox*>::iterator end = cleanLineFloats->end();
-                for (Vector<RenderBox*>::iterator f = cleanLineFloats->begin(); f != end; ++f) {
-                    FloatingObject* floatingObject = insertFloatingObject(*f);
-                    ASSERT(!floatingObject->m_originatingLine);
-                    floatingObject->m_originatingLine = line;
-                    setLogicalHeight(logicalTopForChild(*f) - marginBeforeForChild(*f));
+                for (auto it = cleanLineFloats->begin(), end = cleanLineFloats->end(); it != end; ++it) {
+                    RenderBox* floatingBox = *it;
+                    FloatingObject* floatingObject = insertFloatingObject(*floatingBox);
+                    ASSERT_WITH_SECURITY_IMPLICATION(!floatingObject->originatingLine());
+                    floatingObject->setOriginatingLine(line);
+                    setLogicalHeight(logicalTopForChild(*floatingBox) - marginBeforeForChild(*floatingBox));
                     positionNewFloats();
-                    ASSERT(layoutState.floats()[numCleanFloats].object == *f);
+                    ASSERT(&layoutState.floats()[numCleanFloats].object == floatingBox);
                     numCleanFloats++;
                 }
             }
@@ -2349,17 +1860,17 @@ RootInlineBox* RenderBlock::determineStartPosition(LineLayoutState& layoutState,
         resolver.setPosition(iter, numberOfIsolateAncestors(iter));
         resolver.setStatus(last->lineBreakBidiStatus());
     } else {
-        TextDirection direction = style()->direction();
-        if (style()->unicodeBidi() == Plaintext)
-            determineDirectionality(direction, InlineIterator(this, bidiFirstSkippingEmptyInlines(this), 0));
-        resolver.setStatus(BidiStatus(direction, isOverride(style()->unicodeBidi())));
-        InlineIterator iter = InlineIterator(this, bidiFirstSkippingEmptyInlines(this, &resolver), 0);
+        TextDirection direction = style().direction();
+        if (style().unicodeBidi() == Plaintext)
+            determineDirectionality(direction, InlineIterator(this, bidiFirstSkippingEmptyInlines(*this), 0));
+        resolver.setStatus(BidiStatus(direction, isOverride(style().unicodeBidi())));
+        InlineIterator iter = InlineIterator(this, bidiFirstSkippingEmptyInlines(*this, &resolver), 0);
         resolver.setPosition(iter, numberOfIsolateAncestors(iter));
     }
     return curr;
 }
 
-void RenderBlock::determineEndPosition(LineLayoutState& layoutState, RootInlineBox* startLine, InlineIterator& cleanLineStart, BidiStatus& cleanLineBidiStatus)
+void RenderBlockFlow::determineEndPosition(LineLayoutState& layoutState, RootInlineBox* startLine, InlineIterator& cleanLineStart, BidiStatus& cleanLineBidiStatus)
 {
     ASSERT(!layoutState.endLine());
     size_t floatIndex = layoutState.floatIndex();
@@ -2396,11 +1907,11 @@ void RenderBlock::determineEndPosition(LineLayoutState& layoutState, RootInlineB
     layoutState.setEndLine(last);
 }
 
-bool RenderBlock::checkPaginationAndFloatsAtEndLine(LineLayoutState& layoutState)
+bool RenderBlockFlow::checkPaginationAndFloatsAtEndLine(LineLayoutState& layoutState)
 {
     LayoutUnit lineDelta = logicalHeight() - layoutState.endLineLogicalTop();
 
-    bool paginated = view()->layoutState() && view()->layoutState()->isPaginated();
+    bool paginated = view().layoutState() && view().layoutState()->isPaginated();
     if (paginated && layoutState.flowThread()) {
         // Check all lines from here to the end, and see if the hypothetical new position for the lines will result
         // in a different available line width.
@@ -2409,8 +1920,9 @@ bool RenderBlock::checkPaginationAndFloatsAtEndLine(LineLayoutState& layoutState
                 // This isn't the real move we're going to do, so don't update the line box's pagination
                 // strut yet.
                 LayoutUnit oldPaginationStrut = lineBox->paginationStrut();
+                bool overflowsRegion;
                 lineDelta -= oldPaginationStrut;
-                adjustLinePositionForPagination(lineBox, lineDelta, layoutState.flowThread());
+                adjustLinePositionForPagination(lineBox, lineDelta, overflowsRegion, layoutState.flowThread());
                 lineBox->setPaginationStrut(oldPaginationStrut);
             }
             if (lineWidthForPaginatedLineChanged(lineBox, lineDelta, layoutState.flowThread()))
@@ -2422,7 +1934,7 @@ bool RenderBlock::checkPaginationAndFloatsAtEndLine(LineLayoutState& layoutState
         return true;
     
     // See if any floats end in the range along which we want to shift the lines vertically.
-    LayoutUnit logicalTop = min(logicalHeight(), layoutState.endLineLogicalTop());
+    LayoutUnit logicalTop = std::min(logicalHeight(), layoutState.endLineLogicalTop());
 
     RootInlineBox* lastLine = layoutState.endLine();
     while (RootInlineBox* nextLine = lastLine->nextRootBox())
@@ -2431,17 +1943,29 @@ bool RenderBlock::checkPaginationAndFloatsAtEndLine(LineLayoutState& layoutState
     LayoutUnit logicalBottom = lastLine->lineBottomWithLeading() + absoluteValue(lineDelta);
 
     const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-    FloatingObjectSetIterator end = floatingObjectSet.end();
-    for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-        FloatingObject* f = *it;
-        if (logicalBottomForFloat(f) >= logicalTop && logicalBottomForFloat(f) < logicalBottom)
+    auto end = floatingObjectSet.end();
+    for (auto it = floatingObjectSet.begin(); it != end; ++it) {
+        const auto& floatingObject = *it->get();
+        if (logicalBottomForFloat(floatingObject) >= logicalTop && logicalBottomForFloat(floatingObject) < logicalBottom)
             return false;
     }
 
     return true;
 }
 
-bool RenderBlock::matchedEndLine(LineLayoutState& layoutState, const InlineBidiResolver& resolver, const InlineIterator& endLineStart, const BidiStatus& endLineStatus)
+bool RenderBlockFlow::lineWidthForPaginatedLineChanged(RootInlineBox* rootBox, LayoutUnit lineDelta, RenderFlowThread* flowThread) const
+{
+    if (!flowThread)
+        return false;
+
+    RenderRegion* currentRegion = regionAtBlockOffset(rootBox->lineTopWithLeading() + lineDelta);
+    // Just bail if the region didn't change.
+    if (rootBox->containingRegion() == currentRegion)
+        return false;
+    return rootBox->paginatedLineWidth() != availableLogicalWidthForContent(currentRegion);
+}
+
+bool RenderBlockFlow::matchedEndLine(LineLayoutState& layoutState, const InlineBidiResolver& resolver, const InlineIterator& endLineStart, const BidiStatus& endLineStatus)
 {
     if (resolver.position() == endLineStart) {
         if (resolver.status() != endLineStatus)
@@ -2451,11 +1975,11 @@ bool RenderBlock::matchedEndLine(LineLayoutState& layoutState, const InlineBidiR
 
     // The first clean line doesn't match, but we can check a handful of following lines to try
     // to match back up.
-    static int numLines = 8; // The # of lines we're willing to match against.
+    static const int numLines = 8; // The # of lines we're willing to match against.
     RootInlineBox* originalEndLine = layoutState.endLine();
     RootInlineBox* line = originalEndLine;
     for (int i = 0; i < numLines && line; i++, line = line->nextRootBox()) {
-        if (line->lineBreakObj() == resolver.position().m_obj && line->lineBreakPos() == resolver.position().m_pos) {
+        if (line->lineBreakObj() == resolver.position().renderer() && line->lineBreakPos() == resolver.position().offset() && !line->hasAnonymousInlineBlock()) {
             // We have a match.
             if (line->lineBreakBidiStatus() != resolver.status())
                 return false; // ...but the bidi state doesn't match.
@@ -2469,7 +1993,7 @@ bool RenderBlock::matchedEndLine(LineLayoutState& layoutState, const InlineBidiR
             }
 
             // Now delete the lines that we failed to sync.
-            deleteLineRange(layoutState, renderArena(), originalEndLine, result);
+            deleteLineRange(layoutState, originalEndLine, result);
             return matched;
         }
     }
@@ -2477,80 +2001,6 @@ bool RenderBlock::matchedEndLine(LineLayoutState& layoutState, const InlineBidiR
     return false;
 }
 
-static inline bool skipNonBreakingSpace(const InlineIterator& it, const LineInfo& lineInfo)
-{
-    if (it.m_obj->style()->nbspMode() != SPACE || it.current() != noBreakSpace)
-        return false;
-
-    // FIXME: This is bad.  It makes nbsp inconsistent with space and won't work correctly
-    // with m_minWidth/m_maxWidth.
-    // Do not skip a non-breaking space if it is the first character
-    // on a line after a clean line break (or on the first line, since previousLineBrokeCleanly starts off
-    // |true|).
-    if (lineInfo.isEmpty() && lineInfo.previousLineBrokeCleanly())
-        return false;
-
-    return true;
-}
-
-enum WhitespacePosition { LeadingWhitespace, TrailingWhitespace };
-static inline bool shouldCollapseWhiteSpace(const RenderStyle* style, const LineInfo& lineInfo, WhitespacePosition whitespacePosition)
-{
-    // CSS2 16.6.1
-    // If a space (U+0020) at the beginning of a line has 'white-space' set to 'normal', 'nowrap', or 'pre-line', it is removed.
-    // If a space (U+0020) at the end of a line has 'white-space' set to 'normal', 'nowrap', or 'pre-line', it is also removed.
-    // If spaces (U+0020) or tabs (U+0009) at the end of a line have 'white-space' set to 'pre-wrap', UAs may visually collapse them.
-    return style->collapseWhiteSpace()
-        || (whitespacePosition == TrailingWhitespace && style->whiteSpace() == PRE_WRAP && (!lineInfo.isEmpty() || !lineInfo.previousLineBrokeCleanly()));
-}
-
-static bool requiresLineBoxForContent(RenderInline* flow, const LineInfo& lineInfo)
-{
-    RenderObject* parent = flow->parent();
-    if (flow->document()->inNoQuirksMode() 
-        && (flow->style(lineInfo.isFirstLine())->lineHeight() != parent->style(lineInfo.isFirstLine())->lineHeight()
-        || flow->style()->verticalAlign() != parent->style()->verticalAlign()
-        || !parent->style()->font().fontMetrics().hasIdenticalAscentDescentAndLineGap(flow->style()->font().fontMetrics())))
-        return true;
-    return false;
-}
-
-static bool hasInlineDirectionBordersPaddingOrMargin(RenderInline* flow)
-{
-    // Where an empty inline is split across anonymous blocks we should only give lineboxes to the 'sides' of the
-    // inline that have borders, padding or margin.
-    bool shouldApplyStartBorderPaddingOrMargin = !flow->parent()->isAnonymousBlock() || !flow->isInlineElementContinuation();
-    if (shouldApplyStartBorderPaddingOrMargin && (flow->borderStart() || flow->marginStart() || flow->paddingStart()))
-        return true;
-
-    bool shouldApplyEndBorderPaddingOrMargin = !flow->parent()->isAnonymousBlock() || flow->isInlineElementContinuation() || !flow->inlineElementContinuation();
-    return shouldApplyEndBorderPaddingOrMargin && (flow->borderEnd() || flow->marginEnd() || flow->paddingEnd());
-}
-
-static bool alwaysRequiresLineBox(RenderObject* flow)
-{
-    // FIXME: Right now, we only allow line boxes for inlines that are truly empty.
-    // We need to fix this, though, because at the very least, inlines containing only
-    // ignorable whitespace should should also have line boxes.
-    return isEmptyInline(flow) && hasInlineDirectionBordersPaddingOrMargin(toRenderInline(flow));
-}
-
-static bool requiresLineBox(const InlineIterator& it, const LineInfo& lineInfo = LineInfo(), WhitespacePosition whitespacePosition = LeadingWhitespace)
-{
-    if (it.m_obj->isFloatingOrOutOfFlowPositioned())
-        return false;
-
-    if (it.m_obj->isRenderInline() && !alwaysRequiresLineBox(it.m_obj) && !requiresLineBoxForContent(toRenderInline(it.m_obj), lineInfo))
-        return false;
-
-    if (!shouldCollapseWhiteSpace(it.m_obj->style(), lineInfo, whitespacePosition) || it.m_obj->isBR())
-        return true;
-
-    UChar current = it.current();
-    bool notJustWhitespace = current != ' ' && current != '\t' && current != softHyphen && (current != '\n' || it.m_obj->preservesNewline()) && !skipNonBreakingSpace(it, lineInfo);
-    return notJustWhitespace || isEmptyInline(it.m_obj);
-}
-
 bool RenderBlock::generatesLineBoxesForInlineChild(RenderObject* inlineObj)
 {
     ASSERT(inlineObj->parent() == this);
@@ -2563,1059 +2013,90 @@ bool RenderBlock::generatesLineBoxesForInlineChild(RenderObject* inlineObj)
     return !it.atEnd();
 }
 
-// FIXME: The entire concept of the skipTrailingWhitespace function is flawed, since we really need to be building
-// line boxes even for containers that may ultimately collapse away. Otherwise we'll never get positioned
-// elements quite right. In other words, we need to build this function's work into the normal line
-// object iteration process.
-// NB. this function will insert any floating elements that would otherwise
-// be skipped but it will not position them.
-void RenderBlock::LineBreaker::skipTrailingWhitespace(InlineIterator& iterator, const LineInfo& lineInfo)
-{
-    while (!iterator.atEnd() && !requiresLineBox(iterator, lineInfo, TrailingWhitespace)) {
-        RenderObject* object = iterator.m_obj;
-        if (object->isOutOfFlowPositioned())
-            setStaticPositions(m_block, toRenderBox(object));
-        else if (object->isFloating())
-            m_block->insertFloatingObject(toRenderBox(object));
-        iterator.increment();
-    }
-}
-
-void RenderBlock::LineBreaker::skipLeadingWhitespace(InlineBidiResolver& resolver, LineInfo& lineInfo,
-                                                     FloatingObject* lastFloatFromPreviousLine, LineWidth& width)
+void RenderBlockFlow::addOverflowFromInlineChildren()
 {
-    while (!resolver.position().atEnd() && !requiresLineBox(resolver.position(), lineInfo, LeadingWhitespace)) {
-        RenderObject* object = resolver.position().m_obj;
-        if (object->isOutOfFlowPositioned()) {
-            setStaticPositions(m_block, toRenderBox(object));
-            if (object->style()->isOriginalDisplayInlineType()) {
-                resolver.runs().addRun(createRun(0, 1, object, resolver));
-                lineInfo.incrementRunsFromLeadingWhitespace();
-            }
-        } else if (object->isFloating()) {
-            // The top margin edge of a self-collapsing block that clears a float intrudes up into it by the height of the margin,
-            // so in order to place this first child float at the top content edge of the self-collapsing block add the margin back in before placement.
-            LayoutUnit marginOffset = (!object->previousSibling() && m_block->isSelfCollapsingBlock() && m_block->style()->clear() && m_block->getClearDelta(m_block, LayoutUnit())) ? m_block->collapsedMarginBeforeForChild(m_block) : LayoutUnit();
-            LayoutUnit oldLogicalHeight = m_block->logicalHeight();
-            m_block->setLogicalHeight(oldLogicalHeight + marginOffset);
-            m_block->positionNewFloatOnLine(m_block->insertFloatingObject(toRenderBox(object)), lastFloatFromPreviousLine, lineInfo, width);
-            m_block->setLogicalHeight(oldLogicalHeight);
-        } else if (object->isText() && object->style()->hasTextCombine() && object->isCombineText() && !toRenderCombineText(object)->isCombined()) {
-            toRenderCombineText(object)->combineText();
-            if (toRenderCombineText(object)->isCombined())
-                continue;
-        }
-        resolver.increment();
-    }
-    resolver.commitExplicitEmbedding();
-}
-
-// This is currently just used for list markers and inline flows that have line boxes. Neither should
-// have an effect on whitespace at the start of the line.
-static bool shouldSkipWhitespaceAfterStartObject(RenderBlock* block, RenderObject* o, LineMidpointState& lineMidpointState)
-{
-    RenderObject* next = bidiNextSkippingEmptyInlines(block, o);
-    while (next && next->isFloatingOrOutOfFlowPositioned())
-        next = bidiNextSkippingEmptyInlines(block, next);
-
-    if (next && !next->isBR() && next->isText() && toRenderText(next)->textLength() > 0) {
-        RenderText* nextText = toRenderText(next);
-        UChar nextChar = nextText->characterAt(0);
-        if (nextText->style()->isCollapsibleWhiteSpace(nextChar)) {
-            startIgnoringSpaces(lineMidpointState, InlineIterator(0, o, 0));
-            return true;
-        }
-    }
-
-    return false;
-}
-
-static ALWAYS_INLINE float textWidth(RenderText* text, unsigned from, unsigned len, const Font& font, float xPos, bool isFixedPitch, bool collapseWhiteSpace, HashSet<const SimpleFontData*>& fallbackFonts, TextLayout* layout = 0)
-{
-    GlyphOverflow glyphOverflow;
-    if (isFixedPitch || (!from && len == text->textLength()) || text->style()->hasTextCombine())
-        return text->width(from, len, font, xPos, &fallbackFonts, &glyphOverflow);
-
-    if (layout)
-        return Font::width(*layout, from, len, &fallbackFonts);
-
-    TextRun run = RenderBlock::constructTextRun(text, font, text, from, len, text->style());
-    run.setCharactersLength(text->textLength() - from);
-    ASSERT(run.charactersLength() >= run.length());
-
-    run.setCharacterScanForCodePath(!text->canUseSimpleFontCodePath());
-    run.setTabSize(!collapseWhiteSpace, text->style()->tabSize());
-    run.setXPos(xPos);
-    return font.width(run, &fallbackFonts, &glyphOverflow);
-}
-
-static void tryHyphenating(RenderText* text, const Font& font, const AtomicString& localeIdentifier, unsigned consecutiveHyphenatedLines, int consecutiveHyphenatedLinesLimit, int minimumPrefixLimit, int minimumSuffixLimit, unsigned lastSpace, unsigned pos, float xPos, int availableWidth, bool isFixedPitch, bool collapseWhiteSpace, int lastSpaceWordSpacing, InlineIterator& lineBreak, int nextBreakable, bool& hyphenated)
-{
-    // Map 'hyphenate-limit-{before,after}: auto;' to 2.
-    unsigned minimumPrefixLength;
-    unsigned minimumSuffixLength;
-
-    if (minimumPrefixLimit < 0)
-        minimumPrefixLength = 2;
-    else
-        minimumPrefixLength = static_cast<unsigned>(minimumPrefixLimit);
-
-    if (minimumSuffixLimit < 0)
-        minimumSuffixLength = 2;
-    else
-        minimumSuffixLength = static_cast<unsigned>(minimumSuffixLimit);
-
-    if (pos - lastSpace <= minimumSuffixLength)
-        return;
-
-    if (consecutiveHyphenatedLinesLimit >= 0 && consecutiveHyphenatedLines >= static_cast<unsigned>(consecutiveHyphenatedLinesLimit))
-        return;
-
-    int hyphenWidth = measureHyphenWidth(text, font);
-
-    float maxPrefixWidth = availableWidth - xPos - hyphenWidth - lastSpaceWordSpacing;
-    // If the maximum width available for the prefix before the hyphen is small, then it is very unlikely
-    // that an hyphenation opportunity exists, so do not bother to look for it.
-    if (maxPrefixWidth <= font.pixelSize() * 5 / 4)
-        return;
-
-    TextRun run = RenderBlock::constructTextRun(text, font, text, lastSpace, pos - lastSpace, text->style());
-    run.setCharactersLength(text->textLength() - lastSpace);
-    ASSERT(run.charactersLength() >= run.length());
-
-    run.setTabSize(!collapseWhiteSpace, text->style()->tabSize());
-    run.setXPos(xPos + lastSpaceWordSpacing);
-
-    unsigned prefixLength = font.offsetForPosition(run, maxPrefixWidth, false);
-    if (prefixLength < minimumPrefixLength)
-        return;
-
-    prefixLength = lastHyphenLocation(text->characters() + lastSpace, pos - lastSpace, min(prefixLength, pos - lastSpace - minimumSuffixLength) + 1, localeIdentifier);
-    if (!prefixLength || prefixLength < minimumPrefixLength)
-        return;
-
-    // When lastSapce is a space, which it always is except sometimes at the beginning of a line or after collapsed
-    // space, it should not count towards hyphenate-limit-before.
-    if (prefixLength == minimumPrefixLength) {
-        UChar characterAtLastSpace = text->characterAt(lastSpace);
-        if (characterAtLastSpace == ' ' || characterAtLastSpace == '\n' || characterAtLastSpace == '\t' || characterAtLastSpace == noBreakSpace)
-            return;
-    }
-
-    ASSERT(pos - lastSpace - prefixLength >= minimumSuffixLength);
-
-#if !ASSERT_DISABLED
-    HashSet<const SimpleFontData*> fallbackFonts;
-    float prefixWidth = hyphenWidth + textWidth(text, lastSpace, prefixLength, font, xPos, isFixedPitch, collapseWhiteSpace, fallbackFonts) + lastSpaceWordSpacing;
-    ASSERT(xPos + prefixWidth <= availableWidth);
-#else
-    UNUSED_PARAM(isFixedPitch);
-#endif
-
-    lineBreak.moveTo(text, lastSpace + prefixLength, nextBreakable);
-    hyphenated = true;
-}
-
-class TrailingObjects {
-public:
-    TrailingObjects();
-    void setTrailingWhitespace(RenderText*);
-    void clear();
-    void appendBoxIfNeeded(RenderBoxModelObject*);
-
-    enum CollapseFirstSpaceOrNot { DoNotCollapseFirstSpace, CollapseFirstSpace };
-
-    void updateMidpointsForTrailingBoxes(LineMidpointState&, const InlineIterator& lBreak, CollapseFirstSpaceOrNot);
-
-private:
-    RenderText* m_whitespace;
-    Vector<RenderBoxModelObject*, 4> m_boxes;
-};
-
-TrailingObjects::TrailingObjects()
-    : m_whitespace(0)
-{
-}
-
-inline void TrailingObjects::setTrailingWhitespace(RenderText* whitespace)
-{
-    ASSERT(whitespace);
-    m_whitespace = whitespace;
-}
-
-inline void TrailingObjects::clear()
-{
-    m_whitespace = 0;
-    m_boxes.shrink(0); // Use shrink(0) instead of clear() to retain our capacity.
-}
-
-inline void TrailingObjects::appendBoxIfNeeded(RenderBoxModelObject* box)
-{
-    if (m_whitespace)
-        m_boxes.append(box);
-}
-
-void TrailingObjects::updateMidpointsForTrailingBoxes(LineMidpointState& lineMidpointState, const InlineIterator& lBreak, CollapseFirstSpaceOrNot collapseFirstSpace)
-{
-    if (!m_whitespace)
+    if (auto layout = simpleLineLayout()) {
+        ASSERT(!hasOverflowClip());
+        SimpleLineLayout::collectFlowOverflow(*this, *layout);
         return;
-
-    // This object is either going to be part of the last midpoint, or it is going to be the actual endpoint.
-    // In both cases we just decrease our pos by 1 level to exclude the space, allowing it to - in effect - collapse into the newline.
-    if (lineMidpointState.numMidpoints % 2) {
-        // Find the trailing space object's midpoint.
-        int trailingSpaceMidpoint = lineMidpointState.numMidpoints - 1;
-        for ( ; trailingSpaceMidpoint > 0 && lineMidpointState.midpoints[trailingSpaceMidpoint].m_obj != m_whitespace; --trailingSpaceMidpoint) { }
-        ASSERT(trailingSpaceMidpoint >= 0);
-        if (collapseFirstSpace == CollapseFirstSpace)
-            lineMidpointState.midpoints[trailingSpaceMidpoint].m_pos--;
-
-        // Now make sure every single trailingPositionedBox following the trailingSpaceMidpoint properly stops and starts
-        // ignoring spaces.
-        size_t currentMidpoint = trailingSpaceMidpoint + 1;
-        for (size_t i = 0; i < m_boxes.size(); ++i) {
-            if (currentMidpoint >= lineMidpointState.numMidpoints) {
-                // We don't have a midpoint for this box yet.
-                ensureLineBoxInsideIgnoredSpaces(lineMidpointState, m_boxes[i]);
-            } else {
-                ASSERT(lineMidpointState.midpoints[currentMidpoint].m_obj == m_boxes[i]);
-                ASSERT(lineMidpointState.midpoints[currentMidpoint + 1].m_obj == m_boxes[i]);
-            }
-            currentMidpoint += 2;
-        }
-    } else if (!lBreak.m_obj) {
-        ASSERT(m_whitespace->isText());
-        ASSERT(collapseFirstSpace == CollapseFirstSpace);
-        // Add a new end midpoint that stops right at the very end.
-        unsigned length = m_whitespace->textLength();
-        unsigned pos = length >= 2 ? length - 2 : UINT_MAX;
-        InlineIterator endMid(0, m_whitespace, pos);
-        startIgnoringSpaces(lineMidpointState, endMid);
-        for (size_t i = 0; i < m_boxes.size(); ++i) {
-            ensureLineBoxInsideIgnoredSpaces(lineMidpointState, m_boxes[i]);
-        }
-    }
-}
-
-void RenderBlock::LineBreaker::reset()
-{
-    m_positionedObjects.clear();
-    m_hyphenated = false;
-    m_clear = CNONE;
-}
-
-InlineIterator RenderBlock::LineBreaker::nextLineBreak(InlineBidiResolver& resolver, LineInfo& lineInfo, RenderTextInfo& renderTextInfo, FloatingObject* lastFloatFromPreviousLine, unsigned consecutiveHyphenatedLines, WordMeasurements& wordMeasurements)
-{
-#if !ENABLE(CSS_SHAPES)
-    return nextSegmentBreak(resolver, lineInfo, renderTextInfo, lastFloatFromPreviousLine, consecutiveHyphenatedLines, wordMeasurements);
-#else
-    ShapeInsideInfo* shapeInsideInfo = m_block->layoutShapeInsideInfo();
-
-    if (!shapeInsideInfo || !shapeInsideInfo->lineOverlapsShapeBounds())
-        return nextSegmentBreak(resolver, lineInfo, renderTextInfo, lastFloatFromPreviousLine, consecutiveHyphenatedLines, wordMeasurements);
-
-    InlineIterator end = resolver.position();
-    InlineIterator oldEnd = end;
-
-    if (!shapeInsideInfo->hasSegments()) {
-        end = nextSegmentBreak(resolver, lineInfo, renderTextInfo, lastFloatFromPreviousLine, consecutiveHyphenatedLines, wordMeasurements);
-        resolver.setPositionIgnoringNestedIsolates(oldEnd);
-        return oldEnd;
-    }
-
-    const SegmentList& segments = shapeInsideInfo->segments();
-    SegmentRangeList& segmentRanges = shapeInsideInfo->segmentRanges();
-
-    for (unsigned i = 0; i < segments.size() && !end.atEnd(); i++) {
-        InlineIterator segmentStart = resolver.position();
-        end = nextSegmentBreak(resolver, lineInfo, renderTextInfo, lastFloatFromPreviousLine, consecutiveHyphenatedLines, wordMeasurements);
-
-        ASSERT(segmentRanges.size() == i);
-        if (resolver.position().atEnd()) {
-            segmentRanges.append(LineSegmentRange(segmentStart, end));
-            break;
-        }
-        if (resolver.position() == end) {
-            // Nothing fit this segment
-            end = segmentStart;
-            segmentRanges.append(LineSegmentRange(segmentStart, segmentStart));
-            resolver.setPositionIgnoringNestedIsolates(segmentStart);
-        } else {
-            // Note that resolver.position is already skipping some of the white space at the beginning of the line,
-            // so that's why segmentStart might be different than resolver.position().
-            LineSegmentRange range(resolver.position(), end);
-            segmentRanges.append(range);
-            resolver.setPosition(end, numberOfIsolateAncestors(end));
-
-            if (lineInfo.previousLineBrokeCleanly()) {
-                // If we hit a new line break, just stop adding anything to this line.
-                break;
-            }
-        }
-    }
-    resolver.setPositionIgnoringNestedIsolates(oldEnd);
-    return end;
-#endif
-}
-
-static inline bool iteratorIsBeyondEndOfRenderCombineText(const InlineIterator& iter, RenderCombineText* renderer)
-{
-    return iter.m_obj == renderer && iter.m_pos >= renderer->textLength();
-}
-
-static inline void commitLineBreakAtCurrentWidth(LineWidth& width, InlineIterator& lBreak, RenderObject* object, unsigned offset = 0, int nextBreak = -1)
-{
-    width.commit();
-    lBreak.moveTo(object, offset, nextBreak);
-}
-
-static bool textBeginsWithBreakablePosition(RenderObject* next)
-{
-    ASSERT(next->isText());
-    RenderText* nextText = toRenderText(next);
-    if (nextText->isWordBreak())
-        return true;
-    if (!nextText->textLength())
-        return false;
-    UChar c = nextText->characterAt(0);
-    return c == ' ' || c == '\t' || (c == '\n' && !nextText->preservesNewline());
-}
-
-static bool canBreakAtThisPosition(bool autoWrap, LineWidth& width, InlineIterator& lBreak, RenderObject* next, const InlineIterator& current, EWhiteSpace currWS, bool currentCharacterIsSpace, bool autoWrapWasEverTrueOnLine)
-{
-    // If we are no-wrap and have found a line-breaking opportunity already then we should take it.
-    if (width.committedWidth() && !width.fitsOnLine(currentCharacterIsSpace) && currWS == NOWRAP)
-        return true;
-
-    // Avoid breaking before empty inlines.
-    if (next && isEmptyInline(next))
-        return false;
-
-    // Return early if we autowrap and the current character is a space as we will always want to break at such a position.
-    if (autoWrap && currentCharacterIsSpace)
-        return true;
-
-    bool nextIsText = (next && (current.m_obj->isText() || isEmptyInline(current.m_obj)) && next->isText() && !next->isBR() && (autoWrap || next->style()->autoWrap()));
-    if (!nextIsText)
-        return autoWrap;
-
-    bool canBreakHere = !currentCharacterIsSpace && textBeginsWithBreakablePosition(next);
-
-    // See if attempting to fit below floats creates more available width on the line.
-    if (!width.fitsOnLine() && !width.committedWidth())
-        width.fitBelowFloats();
-
-    bool canPlaceOnLine = width.fitsOnLine() || !autoWrapWasEverTrueOnLine;
-
-    if (canPlaceOnLine && canBreakHere)
-        commitLineBreakAtCurrentWidth(width, lBreak, next);
-
-    return canBreakHere;
-}
-
-InlineIterator RenderBlock::LineBreaker::nextSegmentBreak(InlineBidiResolver& resolver, LineInfo& lineInfo, RenderTextInfo& renderTextInfo, FloatingObject* lastFloatFromPreviousLine, unsigned consecutiveHyphenatedLines, WordMeasurements& wordMeasurements)
-{
-    reset();
-
-    ASSERT(resolver.position().root() == m_block);
-
-    bool appliedStartWidth = resolver.position().m_pos > 0;
-    bool includeEndWidth = true;
-    LineMidpointState& lineMidpointState = resolver.midpointState();
-
-    LineWidth width(m_block, lineInfo.isFirstLine(), requiresIndent(lineInfo.isFirstLine(), lineInfo.previousLineBrokeCleanly(), m_block->style()));
-
-    skipLeadingWhitespace(resolver, lineInfo, lastFloatFromPreviousLine, width);
-
-    if (resolver.position().atEnd())
-        return resolver.position();
-
-    // This variable is used only if whitespace isn't set to PRE, and it tells us whether
-    // or not we are currently ignoring whitespace.
-    bool ignoringSpaces = false;
-    InlineIterator ignoreStart;
-
-    // This variable tracks whether the very last character we saw was a space.  We use
-    // this to detect when we encounter a second space so we know we have to terminate
-    // a run.
-    bool currentCharacterIsSpace = false;
-    bool currentCharacterIsWS = false;
-    TrailingObjects trailingObjects;
-
-    InlineIterator lBreak = resolver.position();
-
-    // FIXME: It is error-prone to split the position object out like this.
-    // Teach this code to work with objects instead of this split tuple.
-    InlineIterator current = resolver.position();
-    RenderObject* last = current.m_obj;
-    bool atStart = true;
-
-    bool startingNewParagraph = lineInfo.previousLineBrokeCleanly();
-    lineInfo.setPreviousLineBrokeCleanly(false);
-
-    bool autoWrapWasEverTrueOnLine = false;
-    bool floatsFitOnLine = true;
-
-    // Firefox and Opera will allow a table cell to grow to fit an image inside it under
-    // very specific circumstances (in order to match common WinIE renderings).
-    // Not supporting the quirk has caused us to mis-render some real sites. (See Bugzilla 10517.)
-    RenderStyle* blockStyle = m_block->style();
-    bool allowImagesToBreak = !m_block->document()->inQuirksMode() || !m_block->isTableCell() || !blockStyle->logicalWidth().isIntrinsicOrAuto();
-
-    EWhiteSpace currWS = blockStyle->whiteSpace();
-    EWhiteSpace lastWS = currWS;
-    while (current.m_obj) {
-        RenderStyle* currentStyle = current.m_obj->style();
-        RenderObject* next = bidiNextSkippingEmptyInlines(m_block, current.m_obj);
-        if (next && next->parent() && !next->parent()->isDescendantOf(current.m_obj->parent()))
-            includeEndWidth = true;
-
-        currWS = current.m_obj->isReplaced() ? current.m_obj->parent()->style()->whiteSpace() : currentStyle->whiteSpace();
-        lastWS = last->isReplaced() ? last->parent()->style()->whiteSpace() : last->style()->whiteSpace();
-
-        bool autoWrap = RenderStyle::autoWrap(currWS);
-        autoWrapWasEverTrueOnLine = autoWrapWasEverTrueOnLine || autoWrap;
-
-#if ENABLE(SVG)
-        bool preserveNewline = current.m_obj->isSVGInlineText() ? false : RenderStyle::preserveNewline(currWS);
-#else
-        bool preserveNewline = RenderStyle::preserveNewline(currWS);
-#endif
-
-        bool collapseWhiteSpace = RenderStyle::collapseWhiteSpace(currWS);
-
-        if (current.m_obj->isBR()) {
-            if (width.fitsOnLine()) {
-                lBreak.moveToStartOf(current.m_obj);
-                lBreak.increment();
-
-                // A <br> always breaks a line, so don't let the line be collapsed
-                // away. Also, the space at the end of a line with a <br> does not
-                // get collapsed away.  It only does this if the previous line broke
-                // cleanly.  Otherwise the <br> has no effect on whether the line is
-                // empty or not.
-                if (startingNewParagraph)
-                    lineInfo.setEmpty(false, m_block, &width);
-                trailingObjects.clear();
-                lineInfo.setPreviousLineBrokeCleanly(true);
-
-                // A <br> with clearance always needs a linebox in case the lines below it get dirtied later and 
-                // need to check for floats to clear - so if we're ignoring spaces, stop ignoring them and add a
-                // run for this object.
-                if (ignoringSpaces && currentStyle->clear() != CNONE)
-                    ensureLineBoxInsideIgnoredSpaces(lineMidpointState, current.m_obj);
-
-                if (!lineInfo.isEmpty())
-                    m_clear = currentStyle->clear();
-            }
-            goto end;
-        }
-
-        if (current.m_obj->isOutOfFlowPositioned()) {
-            // If our original display wasn't an inline type, then we can
-            // go ahead and determine our static inline position now.
-            RenderBox* box = toRenderBox(current.m_obj);
-            bool isInlineType = box->style()->isOriginalDisplayInlineType();
-            if (!isInlineType)
-                m_block->setStaticInlinePositionForChild(box, m_block->logicalHeight(), m_block->startOffsetForContent(m_block->logicalHeight()));
-            else  {
-                // If our original display was an INLINE type, then we can go ahead
-                // and determine our static y position now.
-                box->layer()->setStaticBlockPosition(m_block->logicalHeight());
-            }
-
-            // If we're ignoring spaces, we have to stop and include this object and
-            // then start ignoring spaces again.
-            if (isInlineType || current.m_obj->container()->isRenderInline()) {
-                if (ignoringSpaces)
-                    ensureLineBoxInsideIgnoredSpaces(lineMidpointState, current.m_obj);
-                trailingObjects.appendBoxIfNeeded(box);
-            } else
-                m_positionedObjects.append(box);
-            width.addUncommittedWidth(inlineLogicalWidth(current.m_obj));
-            // Reset prior line break context characters.
-            renderTextInfo.m_lineBreakIterator.resetPriorContext();
-        } else if (current.m_obj->isFloating()) {
-            RenderBox* floatBox = toRenderBox(current.m_obj);
-            FloatingObject* f = m_block->insertFloatingObject(floatBox);
-            // check if it fits in the current line.
-            // If it does, position it now, otherwise, position
-            // it after moving to next line (in newLine() func)
-            // FIXME: Bug 110372: Properly position multiple stacked floats with non-rectangular shape outside.
-            if (floatsFitOnLine && width.fitsOnLineExcludingTrailingWhitespace(m_block->logicalWidthForFloat(f))) {
-                m_block->positionNewFloatOnLine(f, lastFloatFromPreviousLine, lineInfo, width);
-                if (lBreak.m_obj == current.m_obj) {
-                    ASSERT(!lBreak.m_pos);
-                    lBreak.increment();
-                }
-            } else
-                floatsFitOnLine = false;
-            // Update prior line break context characters, using U+FFFD (OBJECT REPLACEMENT CHARACTER) for floating element.
-            renderTextInfo.m_lineBreakIterator.updatePriorContext(replacementCharacter);
-        } else if (current.m_obj->isRenderInline()) {
-            // Right now, we should only encounter empty inlines here.
-            ASSERT(isEmptyInline(current.m_obj));
-
-            RenderInline* flowBox = toRenderInline(current.m_obj);
-
-            // Now that some inline flows have line boxes, if we are already ignoring spaces, we need
-            // to make sure that we stop to include this object and then start ignoring spaces again.
-            // If this object is at the start of the line, we need to behave like list markers and
-            // start ignoring spaces.
-            bool requiresLineBox = alwaysRequiresLineBox(current.m_obj);
-            if (requiresLineBox || requiresLineBoxForContent(flowBox, lineInfo)) {
-                // An empty inline that only has line-height, vertical-align or font-metrics will only get a
-                // line box to affect the height of the line if the rest of the line is not empty.
-                if (requiresLineBox)
-                    lineInfo.setEmpty(false, m_block, &width);
-                if (ignoringSpaces) {
-                    trailingObjects.clear();
-                    ensureLineBoxInsideIgnoredSpaces(lineMidpointState, current.m_obj);
-                } else if (blockStyle->collapseWhiteSpace() && resolver.position().m_obj == current.m_obj
-                    && shouldSkipWhitespaceAfterStartObject(m_block, current.m_obj, lineMidpointState)) {
-                    // Like with list markers, we start ignoring spaces to make sure that any
-                    // additional spaces we see will be discarded.
-                    currentCharacterIsSpace = true;
-                    currentCharacterIsWS = true;
-                    ignoringSpaces = true;
-                } else {
-                    trailingObjects.appendBoxIfNeeded(flowBox);
-                }
-            }
-
-            width.addUncommittedWidth(inlineLogicalWidth(current.m_obj) + borderPaddingMarginStart(flowBox) + borderPaddingMarginEnd(flowBox));
-        } else if (current.m_obj->isReplaced()) {
-            RenderBox* replacedBox = toRenderBox(current.m_obj);
-
-            if (atStart)
-                width.updateAvailableWidth(replacedBox->logicalHeight());
-
-            // Break on replaced elements if either has normal white-space.
-            if ((autoWrap || RenderStyle::autoWrap(lastWS)) && (!current.m_obj->isImage() || allowImagesToBreak))
-                commitLineBreakAtCurrentWidth(width, lBreak, current.m_obj);
-
-            if (ignoringSpaces)
-                stopIgnoringSpaces(lineMidpointState, InlineIterator(0, current.m_obj, 0));
-
-            lineInfo.setEmpty(false, m_block, &width);
-            ignoringSpaces = false;
-            currentCharacterIsSpace = false;
-            currentCharacterIsWS = false;
-            trailingObjects.clear();
-
-            // Optimize for a common case. If we can't find whitespace after the list
-            // item, then this is all moot.
-            LayoutUnit replacedLogicalWidth = m_block->logicalWidthForChild(replacedBox) + m_block->marginStartForChild(replacedBox) + m_block->marginEndForChild(replacedBox) + inlineLogicalWidth(current.m_obj);
-            if (current.m_obj->isListMarker()) {
-                if (blockStyle->collapseWhiteSpace() && shouldSkipWhitespaceAfterStartObject(m_block, current.m_obj, lineMidpointState)) {
-                    // Like with inline flows, we start ignoring spaces to make sure that any
-                    // additional spaces we see will be discarded.
-                    currentCharacterIsSpace = true;
-                    currentCharacterIsWS = true;
-                    ignoringSpaces = true;
-                }
-                if (toRenderListMarker(current.m_obj)->isInside())
-                    width.addUncommittedWidth(replacedLogicalWidth);
-            } else
-                width.addUncommittedWidth(replacedLogicalWidth);
-            if (current.m_obj->isRubyRun())
-                width.applyOverhang(toRenderRubyRun(current.m_obj), last, next);
-            // Update prior line break context characters, using U+FFFD (OBJECT REPLACEMENT CHARACTER) for replaced element.
-            renderTextInfo.m_lineBreakIterator.updatePriorContext(replacementCharacter);
-        } else if (current.m_obj->isText()) {
-            if (!current.m_pos)
-                appliedStartWidth = false;
-
-            RenderText* t = toRenderText(current.m_obj);
-
-#if ENABLE(SVG)
-            bool isSVGText = t->isSVGInlineText();
-#endif
-
-            // If we have left a no-wrap inline and entered an autowrap inline while ignoring spaces
-            // then we need to mark the start of the autowrap inline as a potential linebreak now. 
-            if (autoWrap && !RenderStyle::autoWrap(lastWS) && ignoringSpaces)
-                commitLineBreakAtCurrentWidth(width, lBreak, current.m_obj);
-
-            if (t->style()->hasTextCombine() && current.m_obj->isCombineText() && !toRenderCombineText(current.m_obj)->isCombined()) {
-                RenderCombineText* combineRenderer = toRenderCombineText(current.m_obj);
-                combineRenderer->combineText();
-                // The length of the renderer's text may have changed. Increment stale iterator positions
-                if (iteratorIsBeyondEndOfRenderCombineText(lBreak, combineRenderer)) {
-                    ASSERT(iteratorIsBeyondEndOfRenderCombineText(resolver.position(), combineRenderer));
-                    lBreak.increment();
-                    resolver.increment();
-                }
-            }
-
-            RenderStyle* style = t->style(lineInfo.isFirstLine());
-            const Font& f = style->font();
-            bool isFixedPitch = f.isFixedPitch();
-            bool canHyphenate = style->hyphens() == HyphensAuto && WebCore::canHyphenate(style->locale());
-
-            unsigned lastSpace = current.m_pos;
-            float wordSpacing = currentStyle->wordSpacing();
-            float lastSpaceWordSpacing = 0;
-            float wordSpacingForWordMeasurement = 0;
-
-            float wrapW = width.uncommittedWidth() + inlineLogicalWidth(current.m_obj, !appliedStartWidth, true);
-            float charWidth = 0;
-            bool breakNBSP = autoWrap && currentStyle->nbspMode() == SPACE;
-            // Auto-wrapping text should wrap in the middle of a word only if it could not wrap before the word,
-            // which is only possible if the word is the first thing on the line, that is, if |w| is zero.
-            bool breakWords = currentStyle->breakWords() && ((autoWrap && !width.committedWidth()) || currWS == PRE);
-            bool midWordBreak = false;
-            bool breakAll = currentStyle->wordBreak() == BreakAllWordBreak && autoWrap;
-            float hyphenWidth = 0;
-#if ENABLE(SVG)
-            if (isSVGText) {
-                breakWords = false;
-                breakAll = false;
-            }
-#endif
-
-            if (t->isWordBreak()) {
-                commitLineBreakAtCurrentWidth(width, lBreak, current.m_obj);
-                ASSERT(current.m_pos == t->textLength());
-            }
-
-            if (renderTextInfo.m_text != t) {
-                updateCounterIfNeeded(t);
-                renderTextInfo.m_text = t;
-                renderTextInfo.m_font = &f;
-                renderTextInfo.m_layout = f.createLayout(t, width.currentWidth(), collapseWhiteSpace);
-                renderTextInfo.m_lineBreakIterator.resetStringAndReleaseIterator(t->text(), style->locale());
-            } else if (renderTextInfo.m_layout && renderTextInfo.m_font != &f) {
-                renderTextInfo.m_font = &f;
-                renderTextInfo.m_layout = f.createLayout(t, width.currentWidth(), collapseWhiteSpace);
-            }
-
-            TextLayout* textLayout = renderTextInfo.m_layout.get();
-
-            // Non-zero only when kerning is enabled and TextLayout isn't used, in which case we measure
-            // words with their trailing space, then subtract its width.
-            HashSet<const SimpleFontData*> fallbackFonts;
-            float wordTrailingSpaceWidth = (f.typesettingFeatures() & Kerning) && !textLayout ? f.width(constructTextRun(t, f, &space, 1, style), &fallbackFonts) + wordSpacing : 0;
-
-            UChar lastCharacter = renderTextInfo.m_lineBreakIterator.lastCharacter();
-            UChar secondToLastCharacter = renderTextInfo.m_lineBreakIterator.secondToLastCharacter();
-            for (; current.m_pos < t->textLength(); current.fastIncrementInTextNode()) {
-                bool previousCharacterIsSpace = currentCharacterIsSpace;
-                bool previousCharacterIsWS = currentCharacterIsWS;
-                UChar c = current.current();
-                currentCharacterIsSpace = c == ' ' || c == '\t' || (!preserveNewline && (c == '\n'));
-
-                if (!collapseWhiteSpace || !currentCharacterIsSpace)
-                    lineInfo.setEmpty(false, m_block, &width);
-
-                if (c == softHyphen && autoWrap && !hyphenWidth && style->hyphens() != HyphensNone) {
-                    hyphenWidth = measureHyphenWidth(t, f, &fallbackFonts);
-                    width.addUncommittedWidth(hyphenWidth);
-                }
-
-                bool applyWordSpacing = false;
-
-                currentCharacterIsWS = currentCharacterIsSpace || (breakNBSP && c == noBreakSpace);
-
-                if ((breakAll || breakWords) && !midWordBreak) {
-                    wrapW += charWidth;
-                    bool midWordBreakIsBeforeSurrogatePair = U16_IS_LEAD(c) && current.m_pos + 1 < t->textLength() && U16_IS_TRAIL(t->characters()[current.m_pos + 1]);
-                    charWidth = textWidth(t, current.m_pos, midWordBreakIsBeforeSurrogatePair ? 2 : 1, f, width.committedWidth() + wrapW, isFixedPitch, collapseWhiteSpace, fallbackFonts, textLayout);
-                    midWordBreak = width.committedWidth() + wrapW + charWidth > width.availableWidth();
-                }
-
-                bool betweenWords = c == '\n' || (currWS != PRE && !atStart && isBreakable(renderTextInfo.m_lineBreakIterator, current.m_pos, current.m_nextBreakablePosition, breakNBSP)
-                    && (style->hyphens() != HyphensNone || (current.previousInSameNode() != softHyphen)));
-
-                if (betweenWords || midWordBreak) {
-                    bool stoppedIgnoringSpaces = false;
-                    if (ignoringSpaces) {
-                        lastSpaceWordSpacing = 0;
-                        if (!currentCharacterIsSpace) {
-                            // Stop ignoring spaces and begin at this
-                            // new point.
-                            ignoringSpaces = false;
-                            wordSpacingForWordMeasurement = 0;
-                            lastSpace = current.m_pos; // e.g., "Foo    goo", don't add in any of the ignored spaces.
-                            stopIgnoringSpaces(lineMidpointState, InlineIterator(0, current.m_obj, current.m_pos));
-                            stoppedIgnoringSpaces = true;
-                        } else {
-                            // Just keep ignoring these spaces.
-                            goto nextCharacter;
-                        }
-                    }
-
-                    wordMeasurements.grow(wordMeasurements.size() + 1);
-                    WordMeasurement& wordMeasurement = wordMeasurements.last();
-                    
-                    wordMeasurement.renderer = t;
-                    wordMeasurement.endOffset = current.m_pos;
-                    wordMeasurement.startOffset = lastSpace;
-                    
-                    float additionalTempWidth;
-                    if (wordTrailingSpaceWidth && c == ' ')
-                        additionalTempWidth = textWidth(t, lastSpace, current.m_pos + 1 - lastSpace, f, width.currentWidth(), isFixedPitch, collapseWhiteSpace, wordMeasurement.fallbackFonts, textLayout) - wordTrailingSpaceWidth;
-                    else
-                        additionalTempWidth = textWidth(t, lastSpace, current.m_pos - lastSpace, f, width.currentWidth(), isFixedPitch, collapseWhiteSpace, wordMeasurement.fallbackFonts, textLayout);
-
-                    if (wordMeasurement.fallbackFonts.isEmpty() && !fallbackFonts.isEmpty())
-                        wordMeasurement.fallbackFonts.swap(fallbackFonts);
-                    fallbackFonts.clear();
-
-                    wordMeasurement.width = additionalTempWidth + wordSpacingForWordMeasurement;
-                    additionalTempWidth += lastSpaceWordSpacing;
-                    width.addUncommittedWidth(additionalTempWidth);
-
-                    if (collapseWhiteSpace && previousCharacterIsSpace && currentCharacterIsSpace && additionalTempWidth)
-                        width.setTrailingWhitespaceWidth(additionalTempWidth);
-
-                    if (!appliedStartWidth) {
-                        width.addUncommittedWidth(inlineLogicalWidth(current.m_obj, true, false));
-                        appliedStartWidth = true;
-                    }
-
-                    applyWordSpacing = wordSpacing && currentCharacterIsSpace;
-
-                    if (!width.committedWidth() && autoWrap && !width.fitsOnLine())
-                        width.fitBelowFloats();
-
-                    if (autoWrap || breakWords) {
-                        // If we break only after white-space, consider the current character
-                        // as candidate width for this line.
-                        bool lineWasTooWide = false;
-                        if (width.fitsOnLine() && currentCharacterIsWS && currentStyle->breakOnlyAfterWhiteSpace() && !midWordBreak) {
-                            float charWidth = textWidth(t, current.m_pos, 1, f, width.currentWidth(), isFixedPitch, collapseWhiteSpace, wordMeasurement.fallbackFonts, textLayout) + (applyWordSpacing ? wordSpacing : 0);
-                            // Check if line is too big even without the extra space
-                            // at the end of the line. If it is not, do nothing.
-                            // If the line needs the extra whitespace to be too long,
-                            // then move the line break to the space and skip all
-                            // additional whitespace.
-                            if (!width.fitsOnLineIncludingExtraWidth(charWidth)) {
-                                lineWasTooWide = true;
-                                lBreak.moveTo(current.m_obj, current.m_pos, current.m_nextBreakablePosition);
-                                skipTrailingWhitespace(lBreak, lineInfo);
-                            }
-                        }
-                        if (lineWasTooWide || !width.fitsOnLine()) {
-                            if (canHyphenate && !width.fitsOnLine()) {
-                                tryHyphenating(t, f, style->locale(), consecutiveHyphenatedLines, blockStyle->hyphenationLimitLines(), style->hyphenationLimitBefore(), style->hyphenationLimitAfter(), lastSpace, current.m_pos, width.currentWidth() - additionalTempWidth, width.availableWidth(), isFixedPitch, collapseWhiteSpace, lastSpaceWordSpacing, lBreak, current.m_nextBreakablePosition, m_hyphenated);
-                                if (m_hyphenated)
-                                    goto end;
-                            }
-                            if (lBreak.atTextParagraphSeparator()) {
-                                if (!stoppedIgnoringSpaces && current.m_pos > 0)
-                                    ensureCharacterGetsLineBox(lineMidpointState, current);
-                                lBreak.increment();
-                                lineInfo.setPreviousLineBrokeCleanly(true);
-                                wordMeasurement.endOffset = lBreak.m_pos;
-                            }
-                            if (lBreak.m_obj && lBreak.m_pos && lBreak.m_obj->isText() && toRenderText(lBreak.m_obj)->textLength() && toRenderText(lBreak.m_obj)->characterAt(lBreak.m_pos - 1) == softHyphen && style->hyphens() != HyphensNone)
-                                m_hyphenated = true;
-                            if (lBreak.m_pos && lBreak.m_pos != (unsigned)wordMeasurement.endOffset && !wordMeasurement.width) {
-                                if (charWidth) {
-                                    wordMeasurement.endOffset = lBreak.m_pos;
-                                    wordMeasurement.width = charWidth;
-                                }
-                            }
-                            // Didn't fit. Jump to the end unless there's still an opportunity to collapse whitespace.
-                            if (ignoringSpaces || !collapseWhiteSpace || !currentCharacterIsSpace || !previousCharacterIsSpace)
-                                goto end;
-                        } else {
-                            if (!betweenWords || (midWordBreak && !autoWrap))
-                                width.addUncommittedWidth(-additionalTempWidth);
-                            if (hyphenWidth) {
-                                // Subtract the width of the soft hyphen out since we fit on a line.
-                                width.addUncommittedWidth(-hyphenWidth);
-                                hyphenWidth = 0;
-                            }
-                        }
-                    }
-
-                    if (c == '\n' && preserveNewline) {
-                        if (!stoppedIgnoringSpaces && current.m_pos > 0)
-                            ensureCharacterGetsLineBox(lineMidpointState, current);
-                        lBreak.moveTo(current.m_obj, current.m_pos, current.m_nextBreakablePosition);
-                        lBreak.increment();
-                        lineInfo.setPreviousLineBrokeCleanly(true);
-                        return lBreak;
-                    }
-
-                    if (autoWrap && betweenWords) {
-                        wrapW = 0;
-                        commitLineBreakAtCurrentWidth(width, lBreak, current.m_obj, current.m_pos, current.m_nextBreakablePosition);
-                        // Auto-wrapping text should not wrap in the middle of a word once it has had an
-                        // opportunity to break after a word.
-                        breakWords = false;
-                    }
-
-                    if (midWordBreak && !U16_IS_TRAIL(c) && !(category(c) & (Mark_NonSpacing | Mark_Enclosing | Mark_SpacingCombining))) {
-                        // Remember this as a breakable position in case
-                        // adding the end width forces a break.
-                        lBreak.moveTo(current.m_obj, current.m_pos, current.m_nextBreakablePosition);
-                        midWordBreak &= (breakWords || breakAll);
-                    }
-
-                    if (betweenWords) {
-                        lastSpaceWordSpacing = applyWordSpacing ? wordSpacing : 0;
-                        wordSpacingForWordMeasurement = (applyWordSpacing && wordMeasurement.width) ? wordSpacing : 0;
-                        lastSpace = current.m_pos;
-                    }
-
-                    if (!ignoringSpaces && currentStyle->collapseWhiteSpace()) {
-                        // If we encounter a newline, or if we encounter a
-                        // second space, we need to go ahead and break up this
-                        // run and enter a mode where we start collapsing spaces.
-                        if (currentCharacterIsSpace && previousCharacterIsSpace) {
-                            ignoringSpaces = true;
-
-                            // We just entered a mode where we are ignoring
-                            // spaces. Create a midpoint to terminate the run
-                            // before the second space.
-                            startIgnoringSpaces(lineMidpointState, ignoreStart);
-                            trailingObjects.updateMidpointsForTrailingBoxes(lineMidpointState, InlineIterator(), TrailingObjects::DoNotCollapseFirstSpace);
-                        }
-                    }
-                } else if (ignoringSpaces) {
-                    // Stop ignoring spaces and begin at this
-                    // new point.
-                    ignoringSpaces = false;
-                    lastSpaceWordSpacing = applyWordSpacing ? wordSpacing : 0;
-                    wordSpacingForWordMeasurement = (applyWordSpacing && wordMeasurements.last().width) ? wordSpacing : 0;
-                    lastSpace = current.m_pos; // e.g., "Foo    goo", don't add in any of the ignored spaces.
-                    stopIgnoringSpaces(lineMidpointState, InlineIterator(0, current.m_obj, current.m_pos));
-                }
-
-#if ENABLE(SVG)
-                if (isSVGText && current.m_pos > 0) {
-                    // Force creation of new InlineBoxes for each absolute positioned character (those that start new text chunks).
-                    if (toRenderSVGInlineText(t)->characterStartsNewTextChunk(current.m_pos))
-                        ensureCharacterGetsLineBox(lineMidpointState, current);
-                }
-#endif
-
-                if (currentCharacterIsSpace && !previousCharacterIsSpace) {
-                    ignoreStart.m_obj = current.m_obj;
-                    ignoreStart.m_pos = current.m_pos;
-                }
-
-                if (!currentCharacterIsWS && previousCharacterIsWS) {
-                    if (autoWrap && currentStyle->breakOnlyAfterWhiteSpace())
-                        lBreak.moveTo(current.m_obj, current.m_pos, current.m_nextBreakablePosition);
-                }
-
-                if (collapseWhiteSpace && currentCharacterIsSpace && !ignoringSpaces)
-                    trailingObjects.setTrailingWhitespace(toRenderText(current.m_obj));
-                else if (!currentStyle->collapseWhiteSpace() || !currentCharacterIsSpace)
-                    trailingObjects.clear();
-
-                atStart = false;
-            nextCharacter:
-                secondToLastCharacter = lastCharacter;
-                lastCharacter = c;
-            }
-
-            renderTextInfo.m_lineBreakIterator.setPriorContext(lastCharacter, secondToLastCharacter);
-
-            wordMeasurements.grow(wordMeasurements.size() + 1);
-            WordMeasurement& wordMeasurement = wordMeasurements.last();
-            wordMeasurement.renderer = t;
-
-            // IMPORTANT: current.m_pos is > length here!
-            float additionalTempWidth = ignoringSpaces ? 0 : textWidth(t, lastSpace, current.m_pos - lastSpace, f, width.currentWidth(), isFixedPitch, collapseWhiteSpace, wordMeasurement.fallbackFonts, textLayout);
-            wordMeasurement.startOffset = lastSpace;
-            wordMeasurement.endOffset = current.m_pos;
-            wordMeasurement.width = ignoringSpaces ? 0 : additionalTempWidth + wordSpacingForWordMeasurement;
-            additionalTempWidth += lastSpaceWordSpacing;
-
-            float inlineLogicalTempWidth = inlineLogicalWidth(current.m_obj, !appliedStartWidth, includeEndWidth);
-            width.addUncommittedWidth(additionalTempWidth + inlineLogicalTempWidth);
-
-            if (wordMeasurement.fallbackFonts.isEmpty() && !fallbackFonts.isEmpty())
-                wordMeasurement.fallbackFonts.swap(fallbackFonts);
-            fallbackFonts.clear();
-
-            if (collapseWhiteSpace && currentCharacterIsSpace && additionalTempWidth)
-                width.setTrailingWhitespaceWidth(additionalTempWidth, inlineLogicalTempWidth);
-
-            includeEndWidth = false;
-
-            if (!width.fitsOnLine()) {
-                if (canHyphenate)
-                    tryHyphenating(t, f, style->locale(), consecutiveHyphenatedLines, blockStyle->hyphenationLimitLines(), style->hyphenationLimitBefore(), style->hyphenationLimitAfter(), lastSpace, current.m_pos, width.currentWidth() - additionalTempWidth, width.availableWidth(), isFixedPitch, collapseWhiteSpace, lastSpaceWordSpacing, lBreak, current.m_nextBreakablePosition, m_hyphenated);
-
-                if (!m_hyphenated && lBreak.previousInSameNode() == softHyphen && style->hyphens() != HyphensNone)
-                    m_hyphenated = true;
-
-                if (m_hyphenated)
-                    goto end;
-            }
-        } else
-            ASSERT_NOT_REACHED();
-
-        bool canBreakHere = canBreakAtThisPosition(autoWrap, width, lBreak, next, current, currWS, currentCharacterIsSpace, autoWrapWasEverTrueOnLine);
-        if (canBreakHere && !width.fitsOnLine(ignoringSpaces)) {
-            // if we have floats, try to get below them.
-            if (currentCharacterIsSpace && !ignoringSpaces && currentStyle->collapseWhiteSpace())
-                trailingObjects.clear();
-
-            if (width.committedWidth())
-                goto end;
-
-            width.fitBelowFloats();
-
-            // |width| may have been adjusted because we got shoved down past a float (thus
-            // giving us more room), so we need to retest, and only jump to
-            // the end label if we still don't fit on the line. -dwh
-            if (!width.fitsOnLine(ignoringSpaces))
-                goto end;
-        } else if (blockStyle->autoWrap() && !width.fitsOnLine() && !width.committedWidth()) {
-            // If the container autowraps but the current child does not then we still need to ensure that it
-            // wraps and moves below any floats.
-            width.fitBelowFloats();
-        }
-
-        if (!current.m_obj->isFloatingOrOutOfFlowPositioned()) {
-            last = current.m_obj;
-            if (last->isReplaced() && autoWrap && (!last->isImage() || allowImagesToBreak) && (!last->isListMarker() || toRenderListMarker(last)->isInside()))
-                commitLineBreakAtCurrentWidth(width, lBreak, next);
-        }
-
-        // Clear out our character space bool, since inline <pre>s don't collapse whitespace
-        // with adjacent inline normal/nowrap spans.
-        if (!collapseWhiteSpace)
-            currentCharacterIsSpace = false;
-
-        current.moveToStartOf(next);
-        atStart = false;
-    }
-
-    if (width.fitsOnLine(true) || lastWS == NOWRAP)
-        lBreak.clear();
-
- end:
-#if ENABLE(CSS_SHAPES)
-    ShapeInsideInfo* shapeInfo = m_block->layoutShapeInsideInfo();
-    bool segmentAllowsOverflow = !shapeInfo || !shapeInfo->hasSegments();
-#else
-    bool segmentAllowsOverflow = true;
-#endif
-
-    if (segmentAllowsOverflow) {
-        if (lBreak == resolver.position()) {
-            if (!lBreak.m_obj || !lBreak.m_obj->isBR()) {
-                // we just add as much as possible
-                if (blockStyle->whiteSpace() == PRE && !current.m_pos) {
-                    lBreak.moveTo(last, last->isText() ? last->length() : 0);
-                } else if (lBreak.m_obj) {
-                    // Don't ever break in the middle of a word if we can help it.
-                    // There's no room at all. We just have to be on this line,
-                    // even though we'll spill out.
-                    lBreak.moveTo(current.m_obj, current.m_pos);
-                }
-            }
-            // make sure we consume at least one char/object.
-            if (lBreak == resolver.position())
-                lBreak.increment();
-        } else if (!width.committedWidth() && (!current.m_obj || !current.m_obj->isBR()) && !current.m_pos) {
-            // Do not push the current object to the next line, when this line has some content, but it is still considered empty.
-            // Empty inline elements like <span></span> can produce such lines and now we just ignore these break opportunities
-            // at the start of a line, if no width has been committed yet.
-            // Behave as if it was actually empty and consume at least one object.
-            lBreak.increment();
-        }
-    }
-
-    // Sanity check our midpoints.
-    checkMidpoints(lineMidpointState, lBreak);
-
-    trailingObjects.updateMidpointsForTrailingBoxes(lineMidpointState, lBreak, TrailingObjects::CollapseFirstSpace);
-
-    // We might have made lBreak an iterator that points past the end
-    // of the object. Do this adjustment to make it point to the start
-    // of the next object instead to avoid confusing the rest of the
-    // code.
-    if (lBreak.m_pos > 0) {
-        lBreak.m_pos--;
-        lBreak.increment();
     }
-
-    return lBreak;
-}
-
-void RenderBlock::addOverflowFromInlineChildren()
-{
     LayoutUnit endPadding = hasOverflowClip() ? paddingEnd() : LayoutUnit();
     // FIXME: Need to find another way to do this, since scrollbars could show when we don't want them to.
-    if (hasOverflowClip() && !endPadding && node() && node()->isRootEditableElement() && style()->isLeftToRightDirection())
+    if (hasOverflowClip() && !endPadding && element() && element()->isRootEditableElement() && style().isLeftToRightDirection())
         endPadding = 1;
     for (RootInlineBox* curr = firstRootBox(); curr; curr = curr->nextRootBox()) {
         addLayoutOverflow(curr->paddedLayoutOverflowRect(endPadding));
-        if (!hasOverflowClip())
-            addVisualOverflow(curr->visualOverflowRect(curr->lineTop(), curr->lineBottom()));
+        RenderRegion* region = flowThreadContainingBlock() ? curr->containingRegion() : nullptr;
+        if (region)
+            region->addLayoutOverflowForBox(this, curr->paddedLayoutOverflowRect(endPadding));
+        if (!hasOverflowClip()) {
+            LayoutRect childVisualOverflowRect = curr->visualOverflowRect(curr->lineTop(), curr->lineBottom());
+            addVisualOverflow(childVisualOverflowRect);
+            if (region)
+                region->addVisualOverflowForBox(this, childVisualOverflowRect);
+        }
     }
 }
 
-void RenderBlock::deleteEllipsisLineBoxes()
+void RenderBlockFlow::deleteEllipsisLineBoxes()
 {
-    ETextAlign textAlign = style()->textAlign();
-    bool ltr = style()->isLeftToRightDirection();
-    bool firstLine = true;
+    ETextAlign textAlign = style().textAlign();
+    bool ltr = style().isLeftToRightDirection();
+    IndentTextOrNot shouldIndentText = IndentText;
     for (RootInlineBox* curr = firstRootBox(); curr; curr = curr->nextRootBox()) {
         if (curr->hasEllipsisBox()) {
             curr->clearTruncation();
 
             // Shift the line back where it belongs if we cannot accomodate an ellipsis.
-            float logicalLeft = pixelSnappedLogicalLeftOffsetForLine(curr->lineTop(), firstLine);
-            float availableLogicalWidth = logicalRightOffsetForLine(curr->lineTop(), false) - logicalLeft;
+            float logicalLeft = logicalLeftOffsetForLine(curr->lineTop(), shouldIndentText);
+            float availableLogicalWidth = logicalRightOffsetForLine(curr->lineTop(), DoNotIndentText) - logicalLeft;
             float totalLogicalWidth = curr->logicalWidth();
-            updateLogicalWidthForAlignment(textAlign, 0, logicalLeft, totalLogicalWidth, availableLogicalWidth, 0);
+            updateLogicalWidthForAlignment(textAlign, curr, 0, logicalLeft, totalLogicalWidth, availableLogicalWidth, 0);
 
             if (ltr)
                 curr->adjustLogicalPosition((logicalLeft - curr->logicalLeft()), 0);
             else
                 curr->adjustLogicalPosition(-(curr->logicalLeft() - logicalLeft), 0);
         }
-        firstLine = false;
+        shouldIndentText = DoNotIndentText;
     }
 }
 
-void RenderBlock::checkLinesForTextOverflow()
+void RenderBlockFlow::checkLinesForTextOverflow()
 {
     // Determine the width of the ellipsis using the current font.
     // FIXME: CSS3 says this is configurable, also need to use 0x002E (FULL STOP) if horizontal ellipsis is "not renderable"
-    const Font& font = style()->font();
-    DEFINE_STATIC_LOCAL(AtomicString, ellipsisStr, (&horizontalEllipsis, 1));
-    const Font& firstLineFont = firstLineStyle()->font();
-    int firstLineEllipsisWidth = firstLineFont.width(constructTextRun(this, firstLineFont, &horizontalEllipsis, 1, firstLineStyle()));
-    int ellipsisWidth = (font == firstLineFont) ? firstLineEllipsisWidth : font.width(constructTextRun(this, font, &horizontalEllipsis, 1, style()));
+    const FontCascade& font = style().fontCascade();
+    static NeverDestroyed<AtomicString> ellipsisStr(&horizontalEllipsis, 1);
+    const FontCascade& firstLineFont = firstLineStyle().fontCascade();
+    float firstLineEllipsisWidth = firstLineFont.width(constructTextRun(this, firstLineFont, &horizontalEllipsis, 1, firstLineStyle()));
+    float ellipsisWidth = (font == firstLineFont) ? firstLineEllipsisWidth : font.width(constructTextRun(this, font, &horizontalEllipsis, 1, style()));
 
     // For LTR text truncation, we want to get the right edge of our padding box, and then we want to see
     // if the right edge of a line box exceeds that.  For RTL, we use the left edge of the padding box and
     // check the left edge of the line box to see if it is less
     // Include the scrollbar for overflow blocks, which means we want to use "contentWidth()"
-    bool ltr = style()->isLeftToRightDirection();
-    ETextAlign textAlign = style()->textAlign();
+    bool ltr = style().isLeftToRightDirection();
+    ETextAlign textAlign = style().textAlign();
     bool firstLine = true;
     for (RootInlineBox* curr = firstRootBox(); curr; curr = curr->nextRootBox()) {
-        // FIXME: Use pixelSnappedLogicalRightOffsetForLine instead of snapping it ourselves once the column workaround in said method has been fixed.
-        // https://bugs.webkit.org/show_bug.cgi?id=105461
-        int blockRightEdge = snapSizeToPixel(logicalRightOffsetForLine(curr->lineTop(), firstLine), curr->x());
-        int blockLeftEdge = pixelSnappedLogicalLeftOffsetForLine(curr->lineTop(), firstLine);
-        int lineBoxEdge = ltr ? snapSizeToPixel(curr->x() + curr->logicalWidth(), curr->x()) : snapSizeToPixel(curr->x(), 0);
+        IndentTextOrNot shouldIndentText = firstLine ? IndentText : DoNotIndentText;
+        LayoutUnit blockRightEdge = logicalRightOffsetForLine(curr->lineTop(), shouldIndentText);
+        LayoutUnit blockLeftEdge = logicalLeftOffsetForLine(curr->lineTop(), shouldIndentText);
+        LayoutUnit lineBoxEdge = ltr ? curr->x() + curr->logicalWidth() : curr->x();
         if ((ltr && lineBoxEdge > blockRightEdge) || (!ltr && lineBoxEdge < blockLeftEdge)) {
             // This line spills out of our box in the appropriate direction.  Now we need to see if the line
             // can be truncated.  In order for truncation to be possible, the line must have sufficient space to
             // accommodate our truncation string, and no replaced elements (images, tables) can overlap the ellipsis
             // space.
-
             LayoutUnit width = firstLine ? firstLineEllipsisWidth : ellipsisWidth;
             LayoutUnit blockEdge = ltr ? blockRightEdge : blockLeftEdge;
             if (curr->lineCanAccommodateEllipsis(ltr, blockEdge, lineBoxEdge, width)) {
                 float totalLogicalWidth = curr->placeEllipsis(ellipsisStr, ltr, blockLeftEdge, blockRightEdge, width);
 
                 float logicalLeft = 0; // We are only interested in the delta from the base position.
-                float truncatedWidth = pixelSnappedLogicalRightOffsetForLine(curr->lineTop(), firstLine);
-                updateLogicalWidthForAlignment(textAlign, 0, logicalLeft, totalLogicalWidth, truncatedWidth, 0);
+                float truncatedWidth = availableLogicalWidthForLine(curr->lineTop(), shouldIndentText);
+                updateLogicalWidthForAlignment(textAlign, curr, nullptr, logicalLeft, totalLogicalWidth, truncatedWidth, 0);
                 if (ltr)
                     curr->adjustLogicalPosition(logicalLeft, 0);
                 else
@@ -3626,7 +2107,7 @@ void RenderBlock::checkLinesForTextOverflow()
     }
 }
 
-bool RenderBlock::positionNewFloatOnLine(FloatingObject* newFloat, FloatingObject* lastFloatFromPreviousLine, LineInfo& lineInfo, LineWidth& width)
+bool RenderBlockFlow::positionNewFloatOnLine(const FloatingObject& newFloat, FloatingObject* lastFloatFromPreviousLine, LineInfo& lineInfo, LineWidth& width)
 {
     if (!positionNewFloats())
         return false;
@@ -3636,39 +2117,43 @@ bool RenderBlock::positionNewFloatOnLine(FloatingObject* newFloat, FloatingObjec
     // We only connect floats to lines for pagination purposes if the floats occur at the start of
     // the line and the previous line had a hard break (so this line is either the first in the block
     // or follows a <br>).
-    if (!newFloat->m_paginationStrut || !lineInfo.previousLineBrokeCleanly() || !lineInfo.isEmpty())
+    if (!newFloat.paginationStrut() || !lineInfo.previousLineBrokeCleanly() || !lineInfo.isEmpty())
         return true;
 
     const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-    ASSERT(floatingObjectSet.last() == newFloat);
+    ASSERT(floatingObjectSet.last().get() == &newFloat);
 
     LayoutUnit floatLogicalTop = logicalTopForFloat(newFloat);
-    int paginationStrut = newFloat->m_paginationStrut;
+    LayoutUnit paginationStrut = newFloat.paginationStrut();
 
     if (floatLogicalTop - paginationStrut != logicalHeight() + lineInfo.floatPaginationStrut())
         return true;
 
-    FloatingObjectSetIterator it = floatingObjectSet.end();
+    auto it = floatingObjectSet.end();
     --it; // Last float is newFloat, skip that one.
-    FloatingObjectSetIterator begin = floatingObjectSet.begin();
+    auto begin = floatingObjectSet.begin();
     while (it != begin) {
         --it;
-        FloatingObject* f = *it;
-        if (f == lastFloatFromPreviousLine)
+        auto& floatingObject = *it->get();
+        if (&floatingObject == lastFloatFromPreviousLine)
             break;
-        if (logicalTopForFloat(f) == logicalHeight() + lineInfo.floatPaginationStrut()) {
-            f->m_paginationStrut += paginationStrut;
-            RenderBox* o = f->m_renderer;
-            setLogicalTopForChild(o, logicalTopForChild(o) + marginBeforeForChild(o) + paginationStrut);
-            if (o->isRenderBlock())
-                toRenderBlock(o)->setChildNeedsLayout(true, MarkOnlyThis);
-            o->layoutIfNeeded();
+        if (logicalTopForFloat(floatingObject) == logicalHeight() + lineInfo.floatPaginationStrut()) {
+            floatingObject.setPaginationStrut(paginationStrut + floatingObject.paginationStrut());
+            RenderBox& floatBox = floatingObject.renderer();
+            setLogicalTopForChild(floatBox, logicalTopForChild(floatBox) + marginBeforeForChild(floatBox) + paginationStrut);
+
+            if (updateRegionRangeForBoxChild(floatBox))
+                floatBox.setNeedsLayout(MarkOnlyThis);
+            else if (is<RenderBlock>(floatBox))
+                downcast<RenderBlock>(floatBox).setChildNeedsLayout(MarkOnlyThis);
+            floatBox.layoutIfNeeded();
+
             // Save the old logical top before calling removePlacedObject which will set
             // isPlaced to false. Otherwise it will trigger an assert in logicalTopForFloat.
-            LayoutUnit oldLogicalTop = logicalTopForFloat(f);
-            m_floatingObjects->removePlacedObject(f);
-            setLogicalTopForFloat(f, oldLogicalTop + paginationStrut);
-            m_floatingObjects->addPlacedObject(f);
+            LayoutUnit oldLogicalTop = logicalTopForFloat(floatingObject);
+            m_floatingObjects->removePlacedObject(&floatingObject);
+            setLogicalTopForFloat(floatingObject, oldLogicalTop + paginationStrut);
+            m_floatingObjects->addPlacedObject(&floatingObject);
         }
     }
 
@@ -3678,46 +2163,105 @@ bool RenderBlock::positionNewFloatOnLine(FloatingObject* newFloat, FloatingObjec
     return true;
 }
 
-LayoutUnit RenderBlock::startAlignedOffsetForLine(LayoutUnit position, bool firstLine)
+LayoutUnit RenderBlockFlow::startAlignedOffsetForLine(LayoutUnit position, IndentTextOrNot shouldIndentText)
 {
-    ETextAlign textAlign = style()->textAlign();
-
-    if (textAlign == TASTART) // FIXME: Handle TAEND here
-        return startOffsetForLine(position, firstLine);
+    ETextAlign textAlign = style().textAlign();
+    bool shouldApplyIndentText = false;
+    switch (textAlign) {
+    case LEFT:
+    case WEBKIT_LEFT:
+        shouldApplyIndentText = style().isLeftToRightDirection();
+        break;
+    case RIGHT:
+    case WEBKIT_RIGHT:
+        shouldApplyIndentText = !style().isLeftToRightDirection();
+        break;
+    case TASTART:
+        shouldApplyIndentText = true;
+        break;
+    default:
+        shouldApplyIndentText = false;
+    }
+    // <rdar://problem/15427571>
+    // https://bugs.webkit.org/show_bug.cgi?id=124522
+    // This quirk is for legacy content that doesn't work properly with the center positioning scheme
+    // being honored (e.g., epubs).
+    if (shouldApplyIndentText || document().settings()->useLegacyTextAlignPositionedElementBehavior()) // FIXME: Handle TAEND here
+        return startOffsetForLine(position, shouldIndentText);
 
     // updateLogicalWidthForAlignment() handles the direction of the block so no need to consider it here
     float totalLogicalWidth = 0;
-    float logicalLeft = logicalLeftOffsetForLine(logicalHeight(), false);
-    float availableLogicalWidth = logicalRightOffsetForLine(logicalHeight(), false) - logicalLeft;
-    updateLogicalWidthForAlignment(textAlign, 0, logicalLeft, totalLogicalWidth, availableLogicalWidth, 0);
+    float logicalLeft = logicalLeftOffsetForLine(logicalHeight(), DoNotIndentText);
+    float availableLogicalWidth = logicalRightOffsetForLine(logicalHeight(), DoNotIndentText) - logicalLeft;
+
+    // FIXME: Bug 129311: We need to pass a valid RootInlineBox here, considering the bidi level used to construct the line.
+    updateLogicalWidthForAlignment(textAlign, 0, 0, logicalLeft, totalLogicalWidth, availableLogicalWidth, 0);
 
-    if (!style()->isLeftToRightDirection())
+    if (!style().isLeftToRightDirection())
         return logicalWidth() - logicalLeft;
     return logicalLeft;
 }
 
-
-void RenderBlock::layoutLineGridBox()
+void RenderBlockFlow::updateRegionForLine(RootInlineBox* lineBox) const
 {
-    if (style()->lineGrid() == RenderStyle::initialLineGrid()) {
-        setLineGridBox(0);
+    ASSERT(lineBox);
+
+    if (!hasRegionRangeInFlowThread())
+        lineBox->clearContainingRegion();
+    else {
+        if (auto containingRegion = regionAtBlockOffset(lineBox->lineTopWithLeading()))
+            lineBox->setContainingRegion(*containingRegion);
+        else
+            lineBox->clearContainingRegion();
+    }
+
+    RootInlineBox* prevLineBox = lineBox->prevRootBox();
+    if (!prevLineBox)
         return;
+
+    // This check is more accurate than the one in |adjustLinePositionForPagination| because it takes into
+    // account just the container changes between lines. The before mentioned function doesn't set the flag
+    // correctly if the line is positioned at the top of the last fragment container.
+    if (lineBox->containingRegion() != prevLineBox->containingRegion())
+        lineBox->setIsFirstAfterPageBreak(true);
+}
+
+void RenderBlockFlow::marginCollapseLinesFromStart(LineLayoutState& layoutState, RootInlineBox* stopLine)
+{
+    // We have to handle an anonymous inline block streak at the start of the block in order to make sure our own margins are
+    // correct. We only have to do this if the children can propagate margins out to us.
+    bool resetLogicalHeight = false;
+    if (layoutState.marginInfo().canCollapseWithMarginBefore()) {
+        RootInlineBox* startLine = firstRootBox();
+        RootInlineBox* curr;
+        for (curr = startLine; curr && curr->hasAnonymousInlineBlock() && layoutState.marginInfo().canCollapseWithMarginBefore(); curr = curr->nextRootBox()) {
+            if (curr == stopLine)
+                return;
+            if (!resetLogicalHeight) {
+                setLogicalHeight(borderAndPaddingBefore());
+                resetLogicalHeight = true;
+            }
+            layoutBlockChild(*curr->anonymousInlineBlock(), layoutState.marginInfo(),
+                layoutState.prevFloatBottomFromAnonymousInlineBlock(), layoutState.maxFloatBottomFromAnonymousInlineBlock());
+        }
     }
     
-    setLineGridBox(0);
+    // Now that we've handled the top of the block, if the stopLine isn't an anonymous block, then we're done.
+    if (!stopLine->hasAnonymousInlineBlock())
+        return;
 
-    RootInlineBox* lineGridBox = new (renderArena()) RootInlineBox(this);
-    lineGridBox->setHasTextChildren(); // Needed to make the line ascent/descent actually be honored in quirks mode.
-    lineGridBox->setConstructed();
-    GlyphOverflowAndFallbackFontsMap textBoxDataMap;
-    VerticalPositionCache verticalPositionCache;
-    lineGridBox->alignBoxesInBlockDirection(logicalHeight(), textBoxDataMap, verticalPositionCache);
-    
-    setLineGridBox(lineGridBox);
+    // Re-run margin collapsing on the block sequence that stopLine is a part of.
+    // First go backwards to get the entire sequence.
+    RootInlineBox* prev = stopLine;
+    for ( ; prev->hasAnonymousInlineBlock(); prev = prev->prevRootBox()) {
+    };
+
+    // Update the block height to the correct state.
+    setLogicalHeight(prev->lineBottomWithLeading());
     
-    // FIXME: If any of the characteristics of the box change compared to the old one, then we need to do a deep dirtying
-    // (similar to what happens when the page height changes). Ideally, though, we only do this if someone is actually snapping
-    // to this grid.
+    // Now run margin collapsing on those lines.
+    for (prev = prev->nextRootBox(); prev != stopLine; prev = prev->nextRootBox())
+        layoutBlockChild(*prev->anonymousInlineBlock(), layoutState.marginInfo(), layoutState.prevFloatBottomFromAnonymousInlineBlock(), layoutState.maxFloatBottomFromAnonymousInlineBlock());
 }
 
 }