OverscrollGlow for mainThread-{BLINK CHANGES}

Source/platform/scroll/ScrollAnimator.cpp

 /*
  * 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 36 matching lines @@
 }
 
 ScrollAnimator::~ScrollAnimator()
 {
 }
 
 ScrollResultOneDimensional ScrollAnimator::scroll(ScrollbarOrientation orientation, ScrollGranularity, float step, float delta)
 {
     float& currentPos = (orientation == HorizontalScrollbar) ? m_currentPosX : m_currentPosY;
     float newPos = clampScrollPosition(orientation, currentPos + step * delta);
+
     if (currentPos == newPos)
-        return ScrollResultOneDimensional(false);
+        return ScrollResultOneDimensional(false, delta);
 
     float usedDelta = (newPos - currentPos) / step;
     currentPos = newPos;
 
     notifyPositionChanged();
 
     return ScrollResultOneDimensional(true, delta - usedDelta);
 }
 
 void ScrollAnimator::scrollToOffsetWithoutAnimation(const FloatPoint& offset)
@@ skipping 93 matching lines @@
 }
 
 float ScrollAnimator::clampScrollPosition(ScrollbarOrientation orientation, float pos)
 {
     float maxScrollPos = m_scrollableArea->maximumScrollPosition(orientation);
     float minScrollPos = m_scrollableArea->minimumScrollPosition(orientation);
     return std::max(std::min(pos, maxScrollPos), minScrollPos);
 }
 
 } // namespace blink