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

Source/core/css/PropertySetCSSStyleDeclaration.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Research In Motion Limited. 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.
  *
@@ skipping 73 matching lines @@
 
         s_shouldDeliver = false;
         if (!s_shouldNotifyInspector) {
             s_currentDecl = 0;
             return;
         }
         // We have to clear internal state before calling Inspector's code.
         PropertySetCSSStyleDeclaration* localCopyStyleDecl = s_currentDecl;
         s_currentDecl = 0;
         s_shouldNotifyInspector = false;
-        if (localCopyStyleDecl->parentElement() && localCopyStyleDecl->parentElement()->document())
-            InspectorInstrumentation::didInvalidateStyleAttr(localCopyStyleDecl->parentElement()->document(), localCopyStyleDecl->parentElement());
+        if (localCopyStyleDecl->parentElement())
+            InspectorInstrumentation::didInvalidateStyleAttr(&localCopyStyleDecl->parentElement()->document(), localCopyStyleDecl->parentElement());
     }
 
     void enqueueMutationRecord()
     {
         s_shouldDeliver = true;
     }
 
     void didInvalidateStyleAttr()
     {
         s_shouldNotifyInspector = true;
@@ skipping 305 matching lines @@
     if (!m_parentElement)
         return;
 
     m_parentElement->setNeedsStyleRecalc(LocalStyleChange);
     m_parentElement->invalidateStyleAttribute();
     StyleAttributeMutationScope(this).didInvalidateStyleAttr();
 }
 
 CSSStyleSheet* InlineCSSStyleDeclaration::parentStyleSheet() const
 {
-    return m_parentElement ? m_parentElement->document()->elementSheet() : 0;
+    return m_parentElement ? m_parentElement->document().elementSheet() : 0;
 }
 
 } // namespace WebCore