Add iterator object to iterate efficiently over an Element's attributes

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 d5625111a087ff83edb211f7b05286c36dbbc153..5929c1f1531823010e44c48f381541461259cbf4 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -169,6 +169,7 @@ public:
     // Internal methods that assume the existence of attribute storage, one should use hasAttributes()
     // before calling them. This is not a trivial getter and its return value should be cached for
     // performance.
+    AttributeIteratorAccessor attributesIterator() const { return elementData()->attributesIterator(); }
     size_t attributeCount() const;
     const Attribute& attributeItem(unsigned index) const;
     const Attribute* getAttributeItem(const QualifiedName&) const;