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 84 matching lines @@
   int source_frame_number() const { return source_frame_number_; }
   void set_source_frame_number(int frame_number) {
     source_frame_number_ = frame_number;
   }
 
   HeadsUpDisplayLayerImpl* hud_layer() { return hud_layer_; }
   void set_hud_layer(HeadsUpDisplayLayerImpl* layer_impl) {
     hud_layer_ = layer_impl;
   }
 
+  // This function may return NULL, it is the caller's responsibility to check.
   LayerImpl* InnerViewportScrollLayer() const;
   // This function may return NULL, it is the caller's responsibility to check.
   LayerImpl* OuterViewportScrollLayer() const;
   gfx::ScrollOffset TotalScrollOffset() const;
   gfx::ScrollOffset TotalMaxScrollOffset() const;
 
   LayerImpl* InnerViewportContainerLayer() const;
   LayerImpl* OuterViewportContainerLayer() const;
   LayerImpl* CurrentlyScrollingLayer() const;
   void SetCurrentlyScrollingLayer(LayerImpl* layer);
@@ skipping 105 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   // and the active tree's size is now out of date.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 69 matching lines @@
                                 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_;
+  scoped_ptr<LayerExternalScrollOffsetListener> layer_scroll_offset_listener_;
   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_