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

Source/core/loader/DocumentLoader.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 377 matching lines @@
     // Don't ask if we are loading an empty URL.
     if (request.url().isEmpty())
         return true;
 
     // We are always willing to show alternate content for unreachable URLs.
     if (m_substituteData.isValid() && !m_substituteData.failingURL().isEmpty())
         return true;
 
     // If we're loading content into a subframe, check against the parent's Content Security Policy
     // and kill the load if that check fails.
-    if (m_frame->ownerElement() && !m_frame->ownerElement()->document()->contentSecurityPolicy()->allowChildFrameFromSource(request.url()))
+    if (m_frame->ownerElement() && !m_frame->ownerElement()->document().contentSecurityPolicy()->allowChildFrameFromSource(request.url()))
         return false;
 
     NavigationPolicy policy = NavigationPolicyCurrentTab;
     m_triggeringAction.specifiesNavigationPolicy(&policy);
     if (policyCheckLoadType != PolicyCheckFragment)
         policy = frameLoader()->client()->decidePolicyForNavigation(request, this, policy);
     if (policy == NavigationPolicyCurrentTab)
         return true;
     if (policy == NavigationPolicyIgnore)
         return false;
@@ skipping 600 matching lines @@
 void DocumentLoader::replaceDocument(const String& source, Document* ownerDocument)
 {
     m_frame->loader()->stopAllLoaders();
     m_writer = createWriterFor(m_frame, ownerDocument, m_frame->document()->url(), mimeType(), m_writer ? m_writer->encoding() : "",  m_writer ? m_writer->encodingWasChosenByUser() : false, true);
     if (!source.isNull())
         m_writer->appendReplacingData(source);
     endWriting(m_writer.get());
 }
 
 } // namespace WebCore