Remove mainthread overhang painting code

Source/core/paint/FramePainter.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 FramePainter_h
 #define FramePainter_h
 
 namespace blink {
 
 class FrameView;
 class GraphicsContext;
 class IntRect;
 class Scrollbar;
 
 class FramePainter {
 public:
     FramePainter(FrameView& frameView) : m_frameView(frameView) { }
 
     void paint(GraphicsContext*, const IntRect&);
     void paintScrollbars(GraphicsContext*, const IntRect&);
     void paintContents(GraphicsContext*, const IntRect& damageRect);
     void paintScrollCorner(GraphicsContext*, const IntRect& cornerRect);
 
 private:
     void paintScrollbar(GraphicsContext*, Scrollbar*, const IntRect&);
-    void paintOverhangAreas(GraphicsContext*, const IntRect& horizontalOverhangArea, const IntRect& verticalOverhangArea, const IntRect& dirtyRect);
-    void calculateAndPaintOverhangAreas(GraphicsContext*, const IntRect& dirtyRect);
-    void paintOverhangAreasInternal(GraphicsContext*, const IntRect& horizontalOverhangArea, const IntRect& verticalOverhangArea, const IntRect& dirtyRect);
 
     FrameView& m_frameView;
     static bool s_inPaintContents;
 };
 
 } // namespace blink
 
 #endif // FramePainter_h