Refactor delegated scrolling in LayerImpl

cc/trees/layer_tree_impl.h

 // Copyright 2012 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_IMPL_H_
 #define CC_TREES_LAYER_TREE_IMPL_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 15 matching lines @@
 class TracedValue;
 }
 }
 
 namespace cc {
 
 class ContextProvider;
 class DebugRectHistory;
 class FrameRateCounter;
 class HeadsUpDisplayLayerImpl;
-class LayerScrollOffsetDelegateProxy;
+class LayerExternalScrollOffsetListener;
+class LayerScrollOffsetDelegate;
 class LayerTreeDebugState;
 class LayerTreeImpl;
 class LayerTreeSettings;
 class MemoryHistory;
 class OutputSurface;
 class PageScaleAnimation;
 class PaintTimeCounter;
 class PictureLayerImpl;
 class Proxy;
 class ResourceProvider;
@@ skipping 209 matching lines @@
   // and the active tree's size is now out of date.
   bool ViewportSizeInvalid() const;
   void SetViewportSizeInvalid();
   void ResetViewportSizeInvalid();
 
   // Useful for debug assertions, probably shouldn't be used for anything else.
   Proxy* proxy() const;
 
   void SetRootLayerScrollOffsetDelegate(
       LayerScrollOffsetDelegate* root_layer_scroll_offset_delegate);
-  void OnRootLayerDelegatedScrollOffsetChanged();
-  void UpdateScrollOffsetDelegate();
-  gfx::ScrollOffset GetDelegatedScrollOffset(LayerImpl* layer);
+  void UpdateRootScrollOffsetDelegate();
+  // Distribute the rool scroll between outer and inner viewport scroll layer.
+  // The outer viewport scroll layer scrolls first.
+  void DistributeRootScrollOffset();
 
   // Call this function when you expect there to be a swap buffer.
   // See swap_promise.h for how to use SwapPromise.
   void QueueSwapPromise(scoped_ptr<SwapPromise> swap_promise);
 
   // Take the |new_swap_promise| and append it to |swap_promise_list_|.
   void PassSwapPromises(ScopedPtrVector<SwapPromise>* new_swap_promise);
   void FinishSwapPromises(CompositorFrameMetadata* metadata);
   void BreakSwapPromises(SwapPromise::DidNotSwapReason reason);
 
@@ skipping 48 matching lines @@
   void set_top_controls_height(float top_controls_height);
   float top_controls_height() const { return top_controls_height_; }
   void PushTopControlsFromMainThread(float top_controls_shown_ratio);
 
   void SetPendingPageScaleAnimation(
       scoped_ptr<PendingPageScaleAnimation> pending_animation);
   scoped_ptr<PendingPageScaleAnimation> TakePendingPageScaleAnimation();
 
   void GatherFrameTimingRequestIds(std::vector<int64_t>* request_ids);
 
+  bool IsExternalFlingActive() const;
+  void DidUpdateScrollOffset(int layer_id);
+
  protected:
   explicit LayerTreeImpl(
       LayerTreeHostImpl* layer_tree_host_impl,
       scoped_refptr<SyncedProperty<ScaleGroup>> page_scale_factor,
       scoped_refptr<SyncedTopControls> top_controls_shown_ratio,
       scoped_refptr<SyncedElasticOverscroll> elastic_overscroll);
   float ClampPageScaleFactorToLimits(float page_scale_factor) const;
   void PushPageScaleFactorAndLimits(const float* page_scale_factor,
                                     float min_page_scale_factor,
                                     float max_page_scale_factor);
   bool SetPageScaleFactorLimits(float min_page_scale_factor,
                                 float max_page_scale_factor);
   void DidUpdatePageScale();
   void HideInnerViewportScrollbarsIfNearMinimumScale();
   void PushTopControls(const float* top_controls_shown_ratio);
   LayerTreeHostImpl* layer_tree_host_impl_;
   int source_frame_number_;
   scoped_ptr<LayerImpl> root_layer_;
   HeadsUpDisplayLayerImpl* hud_layer_;
   LayerImpl* currently_scrolling_layer_;
   LayerScrollOffsetDelegate* root_layer_scroll_offset_delegate_;
-  scoped_ptr<LayerScrollOffsetDelegateProxy>
-      inner_viewport_scroll_delegate_proxy_;
-  scoped_ptr<LayerScrollOffsetDelegateProxy>
-      outer_viewport_scroll_delegate_proxy_;
+  bool is_distributing_root_scroll_;
   SkColor background_color_;
   bool has_transparent_background_;
 
   LayerImpl* overscroll_elasticity_layer_;
   LayerImpl* page_scale_layer_;
   LayerImpl* inner_viewport_scroll_layer_;
   LayerImpl* outer_viewport_scroll_layer_;
 
   LayerSelectionBound selection_start_;
   LayerSelectionBound selection_end_;
@@ skipping 49 matching lines @@
 
   scoped_ptr<PendingPageScaleAnimation> pending_page_scale_animation_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_IMPL_H_