cc: Impl thread scroll on ScrollNode instead of LayerImpl

cc/input/scroll_state.h

 // Copyright 2015 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_SCROLL_STATE_H_
 #define CC_INPUT_SCROLL_STATE_H_
 
 #include <list>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 75 matching lines @@
   bool FullyConsumed() const { return !data_.delta_x && !data_.delta_y; }
 
   void set_caused_scroll(bool x, bool y) {
     data_.caused_scroll_x |= x;
     data_.caused_scroll_y |= y;
   }
 
   bool caused_scroll_x() const { return data_.caused_scroll_x; }
   bool caused_scroll_y() const { return data_.caused_scroll_y; }
 
+  LayerTreeImpl* layer_tree_impl() { return layer_tree_impl_; }
   ScrollStateData* data() { return &data_; }
 
  private:
   ScrollStateData data_;
   LayerTreeImpl* layer_tree_impl_;
   std::list<const ScrollNode*> scroll_chain_;
 };
 
 }  // namespace cc
 
 #endif  // CC_INPUT_SCROLL_STATE_H_