Set a bit on Custom Elements on creation to simplify wrapping

Source/core/dom/ElementRareData.h

Index: Source/core/dom/ElementRareData.h
diff --git a/Source/core/dom/ElementRareData.h b/Source/core/dom/ElementRareData.h
index effc75d7d0dab3ada1bf43866e709a54bb6d6fa9..7e5737507c7da56c1432bf248af9821e6280ee41 100644
--- a/Source/core/dom/ElementRareData.h
+++ b/Source/core/dom/ElementRareData.h
@@ -86,6 +86,9 @@ public:
     unsigned childIndex() const { return m_childIndex; }
     void setChildIndex(unsigned index) { m_childIndex = index; }
 
+    void setIsCustomElement();
+    bool isCustomElement() const { return m_isCustomElement; }
+
     // Manually called by Node::reportMemoryUsage.
     void reportMemoryUsage(MemoryObjectInfo*) const;
 
@@ -151,6 +154,8 @@ private:
     unsigned m_childrenAffectedByForwardPositionalRules : 1;
     unsigned m_childrenAffectedByBackwardPositionalRules : 1;
 
+    unsigned m_isCustomElement : 1;
+
     LayoutSize m_minimumSizeForResizing;
     IntSize m_savedLayerScrollOffset;
     RefPtr<RenderStyle> m_computedStyle;
@@ -193,6 +198,7 @@ inline ElementRareData::ElementRareData(RenderObject* renderer)
     , m_childrenAffectedByDirectAdjacentRules(false)
     , m_childrenAffectedByForwardPositionalRules(false)
     , m_childrenAffectedByBackwardPositionalRules(false)
+    , m_isCustomElement(false)
     , m_minimumSizeForResizing(defaultMinimumSizeForResizing())
 {
 }
@@ -204,6 +210,11 @@ inline ElementRareData::~ElementRareData()
     ASSERT(!m_generatedAfter);
 }
 
+inline void ElementRareData::setIsCustomElement()
+{
+    m_isCustomElement = true;
+}
+
 inline void ElementRareData::setPseudoElement(PseudoId pseudoId, PassRefPtr<PseudoElement> element)
 {
     switch (pseudoId) {