Mac: Delete now-dead elastic overscroll code

Source/platform/scroll/ScrollAnimator.h

 /*
  * Copyright (c) 2010, Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 81 matching lines @@
 
     virtual void didAddVerticalScrollbar(Scrollbar*) { }
     virtual void willRemoveVerticalScrollbar(Scrollbar*) { }
     virtual void didAddHorizontalScrollbar(Scrollbar*) { }
     virtual void willRemoveHorizontalScrollbar(Scrollbar*) { }
 
     virtual bool shouldScrollbarParticipateInHitTesting(Scrollbar*) { return true; }
 
     virtual void notifyContentAreaScrolled(const FloatSize&) { }
 
-    virtual bool isRubberBandInProgress() const { return false; }
-
 protected:
     explicit ScrollAnimator(ScrollableArea*);
 
     virtual void notifyPositionChanged();
 
     ScrollableArea* m_scrollableArea;
     float m_currentPosX; // We avoid using a FloatPoint in order to reduce
     float m_currentPosY; // subclass code complexity.
 
 private:
     float clampScrollPosition(ScrollbarOrientation, float);
 };
 
 } // namespace blink
 
 #endif // ScrollAnimator_h