Have Document::accessSVGExtensions() return a reference

Source/core/dom/Document.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 856 matching lines @@
     void setAnnotatedRegionsDirty(bool f) { m_annotatedRegionsDirty = f; }
     bool annotatedRegionsDirty() const { return m_annotatedRegionsDirty; }
     bool hasAnnotatedRegions () const { return m_hasAnnotatedRegions; }
     void setHasAnnotatedRegions(bool f) { m_hasAnnotatedRegions = f; }
     const Vector<AnnotatedRegionValue>& annotatedRegions() const;
     void setAnnotatedRegions(const Vector<AnnotatedRegionValue>&);
 
     virtual void removeAllEventListeners() OVERRIDE FINAL;
 
     const SVGDocumentExtensions* svgExtensions();
-    SVGDocumentExtensions* accessSVGExtensions();
+    SVGDocumentExtensions& accessSVGExtensions();
 
     void initSecurityContext();
     void initSecurityContext(const DocumentInit&);
     void initContentSecurityPolicy(const ContentSecurityPolicyResponseHeaders&);
 
     bool allowInlineEventHandlers(Node*, EventListener*, const String& contextURL, const WTF::OrdinalNumber& contextLine);
     bool allowExecutingScripts(Node*);
 
     void statePopped(PassRefPtr<SerializedScriptValue>);
 
@@ skipping 508 matching lines @@
 inline bool Node::isDocumentNode() const
 {
     return this == document();
 }
 
 Node* eventTargetNodeForDocument(Document*);
 
 } // namespace WebCore
 
 #endif // Document_h