Let LayerTreeHostImpl::ScrollAnimated scroll the outer viewport.

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 <set>
 #include <string>
 #include <vector>
@@ skipping 169 matching lines @@
   void MouseMoveAt(const gfx::Point& viewport_point) override;
   void PinchGestureBegin() override;
   void PinchGestureUpdate(float magnify_delta,
                           const gfx::Point& anchor) override;
   void PinchGestureEnd() override;
   void StartPageScaleAnimation(const gfx::Vector2d& target_offset,
                                bool anchor_point,
                                float page_scale,
                                base::TimeDelta duration);
   void SetNeedsAnimateInput() override;
-  bool IsCurrentlyScrollingRoot() const override;
+  bool IsCurrentlyScrollingInnerViewport() const override;
   bool IsCurrentlyScrollingLayerAt(
       const gfx::Point& viewport_point,
       InputHandler::ScrollInputType type) const override;
   bool HaveWheelEventHandlersAt(const gfx::Point& viewport_point) override;
   bool DoTouchEventsBlockScrollAt(const gfx::Point& viewport_port) override;
   scoped_ptr<SwapPromiseMonitor> CreateLatencyInfoSwapPromiseMonitor(
       ui::LatencyInfo* latency) override;
   ScrollElasticityHelper* CreateScrollElasticityHelper() override;
 
   // TopControlsManagerClient implementation.
@@ skipping 611 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_