Have Node::ensureRareData() return a reference

Source/core/dom/Element.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2013 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 764 matching lines @@
     void updateNamedItemRegistration(const AtomicString& oldName, const AtomicString& newName);
     void updateExtraNamedItemRegistration(const AtomicString& oldName, const AtomicString& newName);
 
     void unregisterNamedFlowContentNode();
 
     void createUniqueElementData();
 
     bool shouldInvalidateDistributionWhenAttributeChanged(ElementShadow*, const QualifiedName&, const AtomicString&);
 
     ElementRareData* elementRareData() const;
-    ElementRareData* ensureElementRareData();
+    ElementRareData& ensureElementRareData();
 
     void detachAllAttrNodesFromElement();
     void detachAttrNodeFromElementWithValue(Attr*, const AtomicString& value);
     void detachAttrNodeAtIndex(Attr*, size_t index);
 
     bool isJavaScriptURLAttribute(const Attribute&) const;
 
     RefPtr<ElementData> m_elementData;
 };
 
@@ skipping 266 matching lines @@
 
 inline const Attribute* ElementData::attributeItem(unsigned index) const
 {
     RELEASE_ASSERT(index < length());
     return attributeBase() + index;
 }
 
 } // namespace
 
 #endif