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

Source/core/css/CSSDefaultStyleSheets.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 158 matching lines @@
     }
 
     if (!mediaControlsStyleSheet && (isHTMLVideoElement(element) || element->hasTagName(audioTag))) {
         String mediaRules = String(mediaControlsUserAgentStyleSheet, sizeof(mediaControlsUserAgentStyleSheet)) + RenderTheme::theme().extraMediaControlsStyleSheet();
         mediaControlsStyleSheet = parseUASheet(mediaRules);
         defaultStyle->addRulesFromSheet(mediaControlsStyleSheet, screenEval());
         defaultPrintStyle->addRulesFromSheet(mediaControlsStyleSheet, printEval());
         changedDefaultStyle = true;
     }
 
-    if (!fullscreenStyleSheet && FullscreenElementStack::isFullScreen(element->document())) {
+    if (!fullscreenStyleSheet && FullscreenElementStack::isFullScreen(&element->document())) {
         String fullscreenRules = String(fullscreenUserAgentStyleSheet, sizeof(fullscreenUserAgentStyleSheet)) + RenderTheme::theme().extraFullScreenStyleSheet();
         fullscreenStyleSheet = parseUASheet(fullscreenRules);
         defaultStyle->addRulesFromSheet(fullscreenStyleSheet, screenEval());
         defaultQuirksStyle->addRulesFromSheet(fullscreenStyleSheet, screenEval());
         changedDefaultStyle = true;
     }
 
     ASSERT(defaultStyle->features().idsInRules.isEmpty());
     ASSERT(mathMLStyleSheet || defaultStyle->features().siblingRules.isEmpty());
 }
 
 } // namespace WebCore