Clean up forward declarations in core/rendering and core/painting

Source/core/paint/ViewDisplayList.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ViewDisplayList_h
 #define ViewDisplayList_h
 
 #include "core/rendering/PaintPhase.h"
 #include "wtf/HashSet.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class GraphicsContext;
 class RenderObject;
-class RenderLayer;
 
 class DisplayItem {
 public:
     enum Type {
         // DisplayItem types must be kept in sync with PaintPhase.
         DrawingPaintPhaseBlockBackground = 0,
         DrawingPaintPhaseChildBlockBackground = 1,
         DrawingPaintPhaseChildBlockBackgrounds = 2,
         DrawingPaintPhaseFloat = 3,
         DrawingPaintPhaseForeground = 4,
@@ skipping 74 matching lines @@
 
     PaintList m_paintList;
     HashSet<const RenderObject*> m_paintListRenderers;
     HashSet<const RenderObject*> m_invalidated;
     PaintList m_newPaints;
 };
 
 } // namespace blink
 
 #endif // ViewDisplayList_h