Update from https://crrev.com/304121

cc/input/input_handler.h

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_INPUT_INPUT_HANDLER_H_
 #define CC_INPUT_INPUT_HANDLER_H_
 
 #include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/swap_promise_monitor.h"
 #include "cc/input/scrollbar.h"
 
 namespace gfx {
 class Point;
 class PointF;
 class Vector2d;
 class Vector2dF;
 }
 
 namespace ui { struct LatencyInfo; }
 
 namespace cc {
 
 class LayerScrollOffsetDelegate;
+class ScrollElasticityHelper;
+
+struct CC_EXPORT InputHandlerScrollResult {
+  InputHandlerScrollResult();
+  // Did any layer scroll as a result this ScrollBy call?
+  bool did_scroll;
+  // Was any of the scroll delta argument to this ScrollBy call not used?
+  bool did_overscroll_root;
+  // The total overscroll that has been accumulated by all ScrollBy calls that
+  // have had overscroll since the last ScrollBegin call. This resets upon a
+  // ScrollBy with no overscroll.
+  gfx::Vector2dF accumulated_root_overscroll;
+  // The amount of the scroll delta argument to this ScrollBy call that was not
+  // used for scrolling.
+  gfx::Vector2dF unused_scroll_delta;
+};
 
 class CC_EXPORT InputHandlerClient {
  public:
   virtual ~InputHandlerClient() {}
 
   virtual void WillShutdown() = 0;
   virtual void Animate(base::TimeTicks time) = 0;
   virtual void MainThreadHasStoppedFlinging() = 0;
 
-  // Called when scroll deltas reaching the root scrolling layer go unused.
-  // The accumulated overscroll is scoped by the most recent call to
-  // InputHandler::ScrollBegin.
-  virtual void DidOverscroll(const gfx::PointF& causal_event_viewport_point,
-                             const gfx::Vector2dF& accumulated_overscroll,
-                             const gfx::Vector2dF& latest_overscroll_delta) = 0;
-
  protected:
   InputHandlerClient() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(InputHandlerClient);
 };
 
 // The InputHandler is a way for the embedders to interact with the impl thread
 // side of the compositor implementation. There is one InputHandler per
 // LayerTreeHost. To use the input handler, implement the InputHanderClient
@@ skipping 26 matching lines @@
                                    ScrollInputType type) = 0;
 
   virtual ScrollStatus ScrollAnimated(const gfx::Point& viewport_point,
                                       const gfx::Vector2dF& scroll_delta) = 0;
 
   // Scroll the selected layer starting at the given position. If the scroll
   // type given to ScrollBegin was a gesture, then the scroll point and delta
   // should be in viewport (logical pixel) coordinates. Otherwise they are in
   // scrolling layer's (logical pixel) space. If there is no room to move the
   // layer in the requested direction, its first ancestor layer that can be
-  // scrolled will be moved instead. If no layer can be moved in the requested
-  // direction at all, then false is returned. If any layer is moved, then
-  // true is returned.
+  // scrolled will be moved instead. The return value's |did_scroll| field is
+  // set to false if no layer can be moved in the requested direction at all,
+  // and set to true if any layer is moved.
   // If the scroll delta hits the root layer, and the layer can no longer move,
   // the root overscroll accumulated within this ScrollBegin() scope is reported
-  // to the client.
+  // in the return value's |accumulated_overscroll| field.
   // Should only be called if ScrollBegin() returned ScrollStarted.
-  virtual bool ScrollBy(const gfx::Point& viewport_point,
-                        const gfx::Vector2dF& scroll_delta) = 0;
+  virtual InputHandlerScrollResult ScrollBy(
+      const gfx::Point& viewport_point,
+      const gfx::Vector2dF& scroll_delta) = 0;
 
   virtual bool ScrollVerticallyByPage(const gfx::Point& viewport_point,
                                       ScrollDirection direction) = 0;
 
   // Returns ScrollStarted if a layer was being actively being scrolled,
   // ScrollIgnored if not.
   virtual ScrollStatus FlingScrollBegin() = 0;
 
   virtual void MouseMoveAt(const gfx::Point& mouse_position) = 0;
 
@@ skipping 26 matching lines @@
   virtual bool HaveTouchEventHandlersAt(const gfx::Point& viewport_point) = 0;
 
   // Calling CreateLatencyInfoSwapPromiseMonitor() to get a scoped
   // LatencyInfoSwapPromiseMonitor. During the life time of the
   // LatencyInfoSwapPromiseMonitor, if SetNeedsRedraw() or SetNeedsRedrawRect()
   // is called on LayerTreeHostImpl, the original latency info will be turned
   // into a LatencyInfoSwapPromise.
   virtual scoped_ptr<SwapPromiseMonitor> CreateLatencyInfoSwapPromiseMonitor(
       ui::LatencyInfo* latency) = 0;
 
+  virtual ScrollElasticityHelper* CreateScrollElasticityHelper() = 0;
+
  protected:
   InputHandler() {}
   virtual ~InputHandler() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(InputHandler);
 };
 
 }  // namespace cc
 
 #endif  // CC_INPUT_INPUT_HANDLER_H_