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

Source/core/html/HTMLVideoElement.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010 Apple 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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 102 matching lines @@
         } else {
             if (renderer())
                 toRenderImage(renderer())->imageResource()->setImageResource(0);
         }
     } else
         HTMLMediaElement::parseAttribute(name, value);
 }
 
 bool HTMLVideoElement::supportsFullscreen() const
 {
-    Page* page = document() ? document()->page() : 0;
+    Page* page = &document() ? document().page() : 0;
     if (!page)
         return false;
 
     if (!player() || !player()->supportsFullscreen())
         return false;
 
     return true;
 }
 
 unsigned HTMLVideoElement::videoWidth() const
@@ skipping 138 matching lines @@
         return 0;
 
     return player()->droppedFrameCount();
 }
 
 KURL HTMLVideoElement::posterImageURL() const
 {
     String url = stripLeadingAndTrailingHTMLSpaces(imageSourceURL());
     if (url.isEmpty())
         return KURL();
-    return document()->completeURL(url);
+    return document().completeURL(url);
 }
 
 }