Report accurate Overscroll on handleWheel.

Source/core/input/EventHandler.h

 /*
  * Copyright (C) 2006, 2007, 2009, 2010, 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:
  * 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 233 matching lines @@
     // granularity - The units that the  scroll delta parameter is in.
     // startNode - The node to start bubbling the scroll from. If a node can't scroll,
     //             the scroll bubbles up to the containing block.
     // stopNode - On input, if provided and non-null, the node at which we should stop bubbling on input.
     //            On output, if provided and a node was scrolled stopNode will point to that node.
     // delta - The delta to scroll by, in the units of the granularity parameter. (e.g. pixels, lines, pages, etc.)
     // absolutePoint - For wheel scrolls - the location, in absolute coordinates, where the event occured.
     ScrollResultOneDimensional scroll(ScrollDirection, ScrollGranularity, Node* startNode = nullptr, Node** stopNode = nullptr, float delta = 1.0f, IntPoint absolutePoint = IntPoint());
 
     void resetOverscroll(bool didScrollX, bool didScrollY);
-    void handleOverscroll(const ScrollResult&, const PlatformGestureEvent&);
+    void handleOverscroll(const ScrollResult&, const FloatPoint& position = FloatPoint(), const FloatSize& velocity = FloatSize());
 
     void customizedScroll(const Node& startNode, ScrollState&);
 
     TouchAction intersectTouchAction(const TouchAction, const TouchAction);
     TouchAction computeEffectiveTouchAction(const Node&);
 
     HitTestResult hitTestResultInFrame(LocalFrame*, const LayoutPoint&, HitTestRequest::HitTestRequestType hitType = HitTestRequest::ReadOnly | HitTestRequest::Active);
 
     void invalidateClick();
 
@@ skipping 163 matching lines @@
     // scroll sequence in this frame, or any child frames. Only used
     // with ScrollCustomization. If some delta has been consumed, a
     // scroll which shouldn't propagate can't cause any element to
     // scroll other than the |m_previousGestureScrolledNode|.
     bool m_deltaConsumedForScrollSequence;
 };
 
 } // namespace blink
 
 #endif // EventHandler_h