Change Widget subclasses to use a CullRect instead of an IntRect for painting.

third_party/WebKit/Source/platform/scroll/Scrollbar.h

 /*
  * Copyright (C) 2004, 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 89 matching lines @@
     ScrollableArea* scrollableArea() const { return m_scrollableArea; }
 
     int pressedPos() const { return m_pressedPos; }
 
     virtual void setHoveredPart(ScrollbarPart);
     virtual void setPressedPart(ScrollbarPart);
 
     void setProportion(int visibleSize, int totalSize);
     void setPressedPos(int p) { m_pressedPos = p; }
 
-    void paint(GraphicsContext*, const IntRect& damageRect) const final;
+    void paint(GraphicsContext*, const CullRect&) const final;
 
     bool isOverlayScrollbar() const override;
     bool shouldParticipateInHitTesting();
 
     bool isWindowActive() const;
 
     bool gestureEvent(const PlatformGestureEvent&);
 
     // These methods are used for platform scrollbars to give :hover feedback.  They will not get called
     // when the mouse went down in a scrollbar, since it is assumed the scrollbar will start
@@ skipping 84 matching lines @@
     bool isScrollbar() const override { return true; }
 
     float scrollableAreaCurrentPos() const;
 };
 
 DEFINE_TYPE_CASTS(Scrollbar, Widget, widget, widget->isScrollbar(), widget.isScrollbar());
 
 } // namespace blink
 
 #endif // Scrollbar_h