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

Source/core/dom/MouseRelatedEvent.cpp

 /*
  * Copyright (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2001 Tobias Anton (anton@stud.fbi.fh-darmstadt.de)
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2005, 2006, 2008 Apple Inc. 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 123 matching lines @@
 {
     Node* targetNode = target() ? target()->toNode() : 0;
     if (!targetNode)
         return;
 
     // Compute coordinates that are based on the target.
     m_layerLocation = m_pageLocation;
     m_offsetLocation = m_pageLocation;
 
     // Must have an updated render tree for this math to work correctly.
-    targetNode->document()->updateLayoutIgnorePendingStylesheets();
+    targetNode->document().updateLayoutIgnorePendingStylesheets();
 
     // Adjust offsetLocation to be relative to the target's position.
     if (RenderObject* r = targetNode->renderer()) {
         FloatPoint localPos = r->absoluteToLocal(absoluteLocation(), UseTransforms);
         m_offsetLocation = roundedLayoutPoint(localPos);
         float scaleFactor = 1 / pageZoomFactor(this);
         if (scaleFactor != 1.0f)
             m_offsetLocation.scale(scaleFactor, scaleFactor);
     }
 
@@ skipping 66 matching lines @@
 }
 
 int MouseRelatedEvent::y() const
 {
     // FIXME: This is not correct.
     // See Microsoft documentation and <http://www.quirksmode.org/dom/w3c_events.html>.
     return m_clientLocation.y();
 }
 
 } // namespace WebCore