Have Node::document() return a reference instead of a pointer

Source/core/rendering/svg/SVGResourcesCache.cpp

 /*
  * Copyright (C) Research In Motion Limited 2010. 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
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 66 matching lines @@
     HashSet<RenderSVGResourceContainer*> resourceSet;
     resources->buildSetOfResources(resourceSet);
 
     HashSet<RenderSVGResourceContainer*>::iterator end = resourceSet.end();
     for (HashSet<RenderSVGResourceContainer*>::iterator it = resourceSet.begin(); it != end; ++it)
         (*it)->removeClient(object);
 }
 
 static inline SVGResourcesCache* resourcesCacheFromRenderObject(const RenderObject* renderer)
 {
-    Document* document = renderer->document();
-    ASSERT(document);
+    Document& document = renderer->document();
 
-    SVGDocumentExtensions* extensions = document->accessSVGExtensions();
+    SVGDocumentExtensions* extensions = document.accessSVGExtensions();
     ASSERT(extensions);
 
     SVGResourcesCache* cache = extensions->resourcesCache();
     ASSERT(cache);
 
     return cache;
 }
 
 SVGResources* SVGResourcesCache::cachedResourcesForRenderObject(const RenderObject* renderer)
 {
@@ skipping 91 matching lines @@
     // The resource itself may have clients, that need to be notified.
     cache->removeResourcesFromRenderObject(resource);
 
         CacheMap::iterator end = cache->m_cache.end();
         for (CacheMap::iterator it = cache->m_cache.begin(); it != end; ++it) {
         it->value->resourceDestroyed(resource);
 
         // Mark users of destroyed resources as pending resolution based on the id of the old resource.
         Element* resourceElement = toElement(resource->node());
         Element* clientElement = toElement(it->key->node());
-        SVGDocumentExtensions* extensions = clientElement->document()->accessSVGExtensions();
+        SVGDocumentExtensions* extensions = clientElement->document().accessSVGExtensions();
 
         extensions->addPendingResource(resourceElement->fastGetAttribute(HTMLNames::idAttr), clientElement);
     }
 }
 
 }