3 files changed, 27 insertions, 1 deletions
diff --git a/Source/JavaScriptCore/runtime/JSObject.cpp b/Source/JavaScriptCore/runtime/JSObject.cpp
index 32adefd2f..e6f95bdfa 100644
--- a/Source/JavaScriptCore/runtime/JSObject.cpp
+++ b/Source/JavaScriptCore/runtime/JSObject.cpp
@@ -1423,6 +1423,7 @@ bool JSObject::getPropertySpecificValue(ExecState* exec, PropertyName propertyNa
 
 void JSObject::getPropertyNames(JSObject* object, ExecState* exec, PropertyNameArray& propertyNames, EnumerationMode mode)
 {
+    propertyNames.setBaseObject(object);
     object->methodTable()->getOwnPropertyNames(object, exec, propertyNames, mode);
 
     if (object->prototype().isNull())
@@ -1513,7 +1514,12 @@ void JSObject::getOwnPropertyNames(JSObject* object, ExecState* exec, PropertyNa
 void JSObject::getOwnNonIndexPropertyNames(JSObject* object, ExecState* exec, PropertyNameArray& propertyNames, EnumerationMode mode)
 {
     getClassPropertyNames(exec, object->classInfo(), propertyNames, mode, object->staticFunctionsReified());
+
+    bool canCachePropertiesFromStructure = !propertyNames.size();
     object->structure()->getPropertyNamesFromStructure(exec->globalData(), propertyNames, mode);
+
+    if (canCachePropertiesFromStructure)
+        propertyNames.setNumCacheableSlotsForObject(object, propertyNames.size());
 }
 
 double JSObject::toNumber(ExecState* exec) const
diff --git a/Source/JavaScriptCore/runtime/JSPropertyNameIterator.cpp b/Source/JavaScriptCore/runtime/JSPropertyNameIterator.cpp
index 225401fbd..496799501 100644
--- a/Source/JavaScriptCore/runtime/JSPropertyNameIterator.cpp
+++ b/Source/JavaScriptCore/runtime/JSPropertyNameIterator.cpp
@@ -54,7 +54,7 @@ JSPropertyNameIterator* JSPropertyNameIterator::create(ExecState* exec, JSObject
     size_t numCacheableSlots = 0;
     if (!o->structure()->hasNonEnumerableProperties() && !o->structure()->hasGetterSetterProperties()
         && !o->structure()->isUncacheableDictionary() && !o->structure()->typeInfo().overridesGetPropertyNames())
-        numCacheableSlots = o->structure()->totalStorageSize();
+        numCacheableSlots = propertyNames.numCacheableSlots();
     
     JSPropertyNameIterator* jsPropertyNameIterator = new (NotNull, allocateCell<JSPropertyNameIterator>(*exec->heap())) JSPropertyNameIterator(exec, propertyNames.data(), numCacheableSlots);
     jsPropertyNameIterator->finishCreation(exec, propertyNames.data(), o);
diff --git a/Source/JavaScriptCore/runtime/PropertyNameArray.h b/Source/JavaScriptCore/runtime/PropertyNameArray.h
index 89b1af00b..1cdac0049 100644
--- a/Source/JavaScriptCore/runtime/PropertyNameArray.h
+++ b/Source/JavaScriptCore/runtime/PropertyNameArray.h
@@ -55,12 +55,16 @@ namespace JSC {
         PropertyNameArray(JSGlobalData* globalData)
             : m_data(PropertyNameArrayData::create())
             , m_globalData(globalData)
+            , m_numCacheableSlots(0)
+            , m_baseObject(0)
         {
         }
 
         PropertyNameArray(ExecState* exec)
             : m_data(PropertyNameArrayData::create())
             , m_globalData(&exec->globalData())
+            , m_numCacheableSlots(0)
+            , m_baseObject(0)
         {
         }
 
@@ -83,12 +87,28 @@ namespace JSC {
         const_iterator begin() const { return m_data->propertyNameVector().begin(); }
         const_iterator end() const { return m_data->propertyNameVector().end(); }
 
+        size_t numCacheableSlots() const { return m_numCacheableSlots; }
+        void setNumCacheableSlotsForObject(JSObject* object, size_t numCacheableSlots)
+        {
+            if (object != m_baseObject)
+                return;
+            m_numCacheableSlots = numCacheableSlots;
+        }
+        void setBaseObject(JSObject* object)
+        {
+            if (m_baseObject)
+                return;
+            m_baseObject = object;
+        }
+
     private:
         typedef HashSet<StringImpl*, PtrHash<StringImpl*> > IdentifierSet;
 
         RefPtr<PropertyNameArrayData> m_data;
         IdentifierSet m_set;
         JSGlobalData* m_globalData;
+        size_t m_numCacheableSlots;
+        JSObject* m_baseObject;
     };
 
 } // namespace JSC