Move custom element definitions into ElementRareData

Source/core/dom/Element.h

Index: Source/core/dom/Element.h
diff --git a/Source/core/dom/Element.h b/Source/core/dom/Element.h
index 29fb8ab390db2463465ee7f931a010c38e3c7eee..af0ff1d968030386e4ef58b38bfd961d815da3ad 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -43,6 +43,7 @@ class Attr;
 class Attribute;
 class ClientRect;
 class ClientRectList;
+class CustomElementDefinition;
 class DOMStringMap;
 class DOMTokenList;
 class ElementRareData;
@@ -521,6 +522,9 @@ public:
     void clearHasPendingResources() { clearElementFlag(HasPendingResources); }
     virtual void buildPendingResource() { };
 
+    void setCustomElementDefinition(PassRefPtr<CustomElementDefinition>);
+    CustomElementDefinition* customElementDefinition() const;
+
     enum {
         ALLOW_KEYBOARD_INPUT = 1 << 0,
         LEGACY_MOZILLA_REQUEST = 1 << 1,