Move some scroll invalidations to the paint invalidation phase

Source/platform/scroll/ScrollView.h

 /*
  * Copyright (C) 2004, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Holger Hans Peter Freyther
  *
  * 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
@@ skipping 253 matching lines @@
     virtual void paintOverhangAreas(GraphicsContext*, const IntRect& horizontalOverhangArea, const IntRect& verticalOverhangArea, const IntRect& dirtyRect);
 
     virtual void scrollbarExistenceDidChange() = 0;
     // These functions are used to create/destroy scrollbars.
     void setHasHorizontalScrollbar(bool);
     void setHasVerticalScrollbar(bool);
 
     virtual void updateScrollCorner();
     virtual void invalidateScrollCornerRect(const IntRect&) OVERRIDE;
 
-    virtual void scrollContentsIfNeeded();
+    void scrollContentsIfNeeded();
     // Scroll the content by via the compositor.
     virtual bool scrollContentsFastPath(const IntSize& scrollDelta) { return true; }
     // Scroll the content by invalidating everything.
     virtual void scrollContentsSlowPath(const IntRect& updateRect);
 
     void setScrollOrigin(const IntPoint&, bool updatePositionAtAll, bool updatePositionSynchronously);
 
     // Subclassed by FrameView to check the writing-mode of the document.
     virtual bool isVerticalDocument() const { return true; }
     virtual bool isFlippedDocument() const { return false; }
@@ skipping 56 matching lines @@
 
     void calculateOverhangAreasForPainting(IntRect& horizontalOverhangRect, IntRect& verticalOverhangRect);
     void updateOverhangAreas();
 }; // class ScrollView
 
 DEFINE_TYPE_CASTS(ScrollView, Widget, widget, widget->isScrollView(), widget.isScrollView());
 
 } // namespace blink
 
 #endif // ScrollView_h