Refactor root element background painting

Source/core/layout/LayoutView.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 172 matching lines @@
 
     void layoutContent();
 #if ENABLE(ASSERT)
     void checkLayoutState();
 #endif
 
     friend class ForceHorriblySlowRectMapping;
 
     bool shouldUsePrintingLayout() const;
 
-    LayoutObject* backgroundLayoutObject() const;
-
     int viewLogicalWidthForBoxSizing() const;
     int viewLogicalHeightForBoxSizing() const;
 
     FrameView* m_frameView;
 
     LayoutObject* m_selectionStart;
     LayoutObject* m_selectionEnd;
 
     int m_selectionStartPos;
     int m_selectionEndPos;
@@ skipping 36 matching lines @@
             m_paintInvalidationState->m_cachedOffsetsEnabled = true;
     }
 private:
     const PaintInvalidationState* m_paintInvalidationState;
     bool m_didDisable;
 };
 
 } // namespace blink
 
 #endif // LayoutView_h