Implement windows mousewheel scroll by page functionality

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 "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time.h"
@@ skipping 73 matching lines @@
       Proxy* proxy,
       RenderingStatsInstrumentation* rendering_stats_instrumentation);
   virtual ~LayerTreeHostImpl();
 
   // InputHandlerClient implementation
   virtual InputHandlerClient::ScrollStatus ScrollBegin(
       gfx::Point viewport_point,
       InputHandlerClient::ScrollInputType type) OVERRIDE;
   virtual bool ScrollBy(gfx::Point viewport_point,
                         gfx::Vector2dF scroll_delta) OVERRIDE;
+  virtual bool ScrollVerticallyByPage(
+      gfx::Point viewport_point,
+      WebKit::WebScrollbar::ScrollDirection direction) OVERRIDE;

[enne (OOO), 2013/03/23 00:25:51]

I know we already depend on a lot of WebScrollbar-related things in cc, but do
we have to add more dependencies?

   virtual void ScrollEnd() OVERRIDE;
   virtual void PinchGestureBegin() OVERRIDE;
   virtual void PinchGestureUpdate(float magnify_delta,
                                   gfx::Point anchor) OVERRIDE;
   virtual void PinchGestureEnd() OVERRIDE;
   virtual void StartPageScaleAnimation(gfx::Vector2d target_offset,
                                        bool anchor_point,
                                        float page_scale,
                                        base::TimeTicks start_time,
                                        base::TimeDelta duration) OVERRIDE;
@@ skipping 346 matching lines @@
   scoped_ptr<AnimationRegistrar> animation_registrar_;
 
   RenderingStatsInstrumentation* rendering_stats_instrumentation_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_