Implement Wheel Gesture Scrolling on OSX.

cc/trees/layer_tree_host_impl.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_TREES_LAYER_TREE_HOST_IMPL_H_
 #define CC_TREES_LAYER_TREE_HOST_IMPL_H_
 
 #include <stddef.h>
 
 #include <set>
@@ skipping 149 matching lines @@
   ~LayerTreeHostImpl() override;
 
   // InputHandler implementation
   void BindToClient(InputHandlerClient* client) override;
   InputHandler::ScrollStatus ScrollBegin(
       ScrollState* scroll_state,
       InputHandler::ScrollInputType type) override;
   InputHandler::ScrollStatus RootScrollBegin(
       ScrollState* scroll_state,
       InputHandler::ScrollInputType type) override;
+  ScrollStatus ScrollAnimatedBegin(const gfx::Point& viewport_point) override;
   InputHandler::ScrollStatus ScrollAnimated(
       const gfx::Point& viewport_point,
       const gfx::Vector2dF& scroll_delta) override;
   void ApplyScroll(LayerImpl* layer, ScrollState* scroll_state);
   InputHandlerScrollResult ScrollBy(ScrollState* scroll_state) override;
   bool ScrollVerticallyByPage(const gfx::Point& viewport_point,
                               ScrollDirection direction) override;
   void RequestUpdateForSynchronousInputHandler() override;
   void SetSynchronousInputHandlerRootScrollOffset(
       const gfx::ScrollOffset& root_offset) override;
@@ skipping 662 matching lines @@
   scoped_ptr<FrameTimingTracker> frame_timing_tracker_;
 
   scoped_ptr<Viewport> viewport_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_