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diff --git a/Source/JavaScriptCore/bytecode/StructureStubClearingWatchpoint.cpp b/Source/JavaScriptCore/bytecode/StructureStubClearingWatchpoint.cpp
new file mode 100644
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+++ b/Source/JavaScriptCore/bytecode/StructureStubClearingWatchpoint.cpp
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+/*
+ * Copyright (C) 2012, 2015 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#include "config.h"
+#include "StructureStubClearingWatchpoint.h"
+
+#if ENABLE(JIT)
+
+#include "CodeBlock.h"
+#include "JSCInlines.h"
+#include "StructureStubInfo.h"
+
+namespace JSC {
+
+StructureStubClearingWatchpoint::~StructureStubClearingWatchpoint() { }
+
+StructureStubClearingWatchpoint* StructureStubClearingWatchpoint::push(
+    const ObjectPropertyCondition& key,
+    WatchpointsOnStructureStubInfo& holder,
+    std::unique_ptr<StructureStubClearingWatchpoint>& head)
+{
+    head = std::make_unique<StructureStubClearingWatchpoint>(key, holder, WTF::move(head));
+    return head.get();
+}
+
+void StructureStubClearingWatchpoint::fireInternal(const FireDetail&)
+{
+    if (!m_key || !m_key.isWatchable(PropertyCondition::EnsureWatchability)) {
+        // This will implicitly cause my own demise: stub reset removes all watchpoints.
+        // That works, because deleting a watchpoint removes it from the set's list, and
+        // the set's list traversal for firing is robust against the set changing.
+        m_holder.codeBlock()->resetStub(*m_holder.stubInfo());
+        return;
+    }
+
+    if (m_key.kind() == PropertyCondition::Presence) {
+        // If this was a presence condition, let's watch the property for replacements. This is profitable
+        // for the DFG, which will want the replacement set to be valid in order to do constant folding.
+        VM& vm = *Heap::heap(m_key.object())->vm();
+        m_key.object()->structure()->startWatchingPropertyForReplacements(vm, m_key.offset());
+    }
+
+    m_key.object()->structure()->addTransitionWatchpoint(this);
+}
+
+WatchpointsOnStructureStubInfo::~WatchpointsOnStructureStubInfo()
+{
+}
+
+StructureStubClearingWatchpoint* WatchpointsOnStructureStubInfo::addWatchpoint(const ObjectPropertyCondition& key)
+{
+    return StructureStubClearingWatchpoint::push(key, *this, m_head);
+}
+
+StructureStubClearingWatchpoint* WatchpointsOnStructureStubInfo::ensureReferenceAndAddWatchpoint(
+    RefPtr<WatchpointsOnStructureStubInfo>& holderRef, CodeBlock* codeBlock,
+    StructureStubInfo* stubInfo, const ObjectPropertyCondition& key)
+{
+    if (!holderRef)
+        holderRef = adoptRef(new WatchpointsOnStructureStubInfo(codeBlock, stubInfo));
+    else {
+        ASSERT(holderRef->m_codeBlock == codeBlock);
+        ASSERT(holderRef->m_stubInfo == stubInfo);
+    }
+    
+    return holderRef->addWatchpoint(key);
+}
+
+} // namespace JSC
+
+#endif // ENABLE(JIT)
+