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

Source/web/ValidationMessageClientImpl.cpp

 /*
  * Copyright (C) 2012 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.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 46 matching lines @@
 }
 
 ValidationMessageClientImpl::~ValidationMessageClientImpl()
 {
     if (m_currentAnchor)
         hideValidationMessage(*m_currentAnchor);
 }
 
 FrameView* ValidationMessageClientImpl::currentView()
 {
-    return m_currentAnchor->document()->view();
+    return m_currentAnchor->document().view();
 }
 
 void ValidationMessageClientImpl::showValidationMessage(const Element& anchor, const String& message)
 {
     if (message.isEmpty()) {
         hideValidationMessage(anchor);
         return;
     }
     if (!anchor.renderBox())
         return;
@@ skipping 29 matching lines @@
     m_client.hideValidationMessage();
 }
 
 bool ValidationMessageClientImpl::isValidationMessageVisible(const Element& anchor)
 {
     return m_currentAnchor == &anchor;
 }
 
 void ValidationMessageClientImpl::documentDetached(const Document& document)
 {
-    if (m_currentAnchor && m_currentAnchor->document() == &document)
+    if (m_currentAnchor && &m_currentAnchor->document() == &document)
         hideValidationMessage(*m_currentAnchor);
 }
 
 void ValidationMessageClientImpl::checkAnchorStatus(Timer<ValidationMessageClientImpl>*)
 {
     ASSERT(m_currentAnchor);
     if (monotonicallyIncreasingTime() >= m_finishTime || !currentView()) {
         hideValidationMessage(*m_currentAnchor);
         return;
     }
 
     // Check the visibility of the element.
     // FIXME: Can we check invisibility by scrollable non-frame elements?
     IntRect newAnchorRect = currentView()->contentsToRootView(m_currentAnchor->pixelSnappedBoundingBox());
     newAnchorRect = intersection(currentView()->convertToRootView(currentView()->boundsRect()), newAnchorRect);
     if (newAnchorRect.isEmpty()) {
         hideValidationMessage(*m_currentAnchor);
         return;
     }
 
     IntRect newAnchorRectInScreen = currentView()->hostWindow()->rootViewToScreen(newAnchorRect);
     if (newAnchorRectInScreen == m_lastAnchorRectInScreen && m_webView.pageScaleFactor() == m_lastPageScaleFactor)
         return;
     m_lastAnchorRectInScreen = newAnchorRectInScreen;
     m_lastPageScaleFactor = m_webView.pageScaleFactor();
     m_client.moveValidationMessage(newAnchorRect);
 }
 
 }