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

Source/core/rendering/RenderView.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 161 matching lines @@
     bool rootBackgroundIsEntirelyFixed() const;
 
     bool hasRenderNamedFlowThreads() const;
     bool checkTwoPassLayoutForAutoHeightRegions() const;
     FlowThreadController* flowThreadController();
 
     void styleDidChange(StyleDifference, const RenderStyle* oldStyle);
 
     IntervalArena* intervalArena();
 
-    IntSize viewportSize() const { return document()->viewportSize(); }
+    IntSize viewportSize() const { return document().viewportSize(); }
 
     void setRenderQuoteHead(RenderQuote* head) { m_renderQuoteHead = head; }
     RenderQuote* renderQuoteHead() const { return m_renderQuoteHead; }
 
     // FIXME: This is a work around because the current implementation of counters
     // requires walking the entire tree repeatedly and most pages don't actually use either
     // feature so we shouldn't take the performance hit when not needed. Long term we should
     // rewrite the counter and quotes code.
     void addRenderCounter() { m_renderCounterCount++; }
     void removeRenderCounter() { ASSERT(m_renderCounterCount > 0); m_renderCounterCount--; }
@@ skipping 202 matching lines @@
     RenderObject::FlowThreadState m_flowThreadState;
     bool m_fragmenting;
 #ifndef NDEBUG
     LayoutState* m_layoutState;
 #endif
 };
 
 } // namespace WebCore
 
 #endif // RenderView_h