Notify ProgrammaticScrollAnimator about scroll layer destruction

Source/platform/scroll/ScrollableArea.cpp

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  * Copyright (C) 2008, 2011 Apple 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.
@@ skipping 402 matching lines @@
 bool ScrollableArea::hasLayerForVerticalScrollbar() const
 {
     return layerForVerticalScrollbar();
 }
 
 bool ScrollableArea::hasLayerForScrollCorner() const
 {
     return layerForScrollCorner();
 }
 
+void ScrollableArea::layerForScrollingDidChange()
+{
+    if (ProgrammaticScrollAnimator* programmaticScrollAnimator = existingProgrammaticScrollAnimator())
+        programmaticScrollAnimator->layerForCompositedScrollingDidChange();
+}
+
 bool ScrollableArea::scheduleAnimation()
 {
     if (HostWindow* window = hostWindow()) {
         window->scheduleAnimation();
         return true;
     }
     return false;
 }
 
 void ScrollableArea::serviceScrollAnimations(double monotonicTime)
@@ skipping 72 matching lines @@
 {
     return scrollSize(orientation);
 }
 
 float ScrollableArea::pixelStep(ScrollbarOrientation) const
 {
     return 1;
 }
 
 } // namespace blink