Make LayerScrollOffsetDelegate updates consistent.

cc/layers/layer_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_LAYERS_LAYER_IMPL_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <set>
 #include <string>
 
@@ skipping 47 matching lines @@
 enum DrawMode {
   DRAW_MODE_NONE,
   DRAW_MODE_HARDWARE,
   DRAW_MODE_SOFTWARE,
   DRAW_MODE_RESOURCELESS_SOFTWARE
 };
 
 class CC_EXPORT LayerImpl : public LayerAnimationValueObserver,
                             public LayerAnimationValueProvider {
  public:
+  // Allows for the ownership of the total scroll offset to be delegated outside
+  // of the layer.
+  class ScrollOffsetDelegate {
+   public:
+    virtual void SetTotalScrollOffset(const gfx::Vector2dF& new_value) = 0;
+    virtual gfx::Vector2dF GetTotalScrollOffset() = 0;
+    virtual bool IsExternalFlingActive() const = 0;
+  };
+
   typedef LayerImplList RenderSurfaceListType;
   typedef LayerImplList LayerListType;
   typedef RenderSurfaceImpl RenderSurfaceType;
 
   enum RenderingContextConstants { NO_RENDERING_CONTEXT = 0 };
 
   static scoped_ptr<LayerImpl> Create(LayerTreeImpl* tree_impl, int id) {
     return make_scoped_ptr(new LayerImpl(tree_impl, id));
   }
 
@@ skipping 276 matching lines @@
 
   virtual void CalculateContentsScale(float ideal_contents_scale,
                                       float device_scale_factor,
                                       float page_scale_factor,
                                       float maximum_animation_contents_scale,
                                       bool animating_transform_to_screen,
                                       float* contents_scale_x,
                                       float* contents_scale_y,
                                       gfx::Size* content_bounds);
 
-  void SetScrollOffsetDelegate(
-      LayerScrollOffsetDelegate* scroll_offset_delegate);
+  void SetScrollOffsetDelegate(ScrollOffsetDelegate* scroll_offset_delegate);
   bool IsExternalFlingActive() const;
 
   void SetScrollOffset(const gfx::Vector2d& scroll_offset);
   void SetScrollOffsetAndDelta(const gfx::Vector2d& scroll_offset,
                                const gfx::Vector2dF& scroll_delta);
   gfx::Vector2d scroll_offset() const { return scroll_offset_; }
 
   gfx::Vector2d MaxScrollOffset() const;
   gfx::Vector2dF ClampScrollToMaxScrollOffset();
   void SetScrollbarPosition(ScrollbarLayerImplBase* scrollbar_layer,
@@ skipping 211 matching lines @@
   scoped_ptr<LayerImpl> replica_layer_;
   int layer_id_;
   LayerTreeImpl* layer_tree_impl_;
 
   // Properties synchronized from the associated Layer.
   gfx::PointF anchor_point_;
   float anchor_point_z_;
   gfx::Size bounds_;
   gfx::SizeF temporary_impl_bounds_;
   gfx::Vector2d scroll_offset_;
-  LayerScrollOffsetDelegate* scroll_offset_delegate_;
+  ScrollOffsetDelegate* scroll_offset_delegate_;
   LayerImpl* scroll_clip_layer_;
   bool scrollable_ : 1;
   bool should_scroll_on_main_thread_ : 1;
   bool have_wheel_event_handlers_ : 1;
   bool have_scroll_event_handlers_ : 1;
   bool user_scrollable_horizontal_ : 1;
   bool user_scrollable_vertical_ : 1;
   bool stacking_order_changed_ : 1;
   // Whether the "back" of this layer should draw.
   bool double_sided_ : 1;
@@ skipping 77 matching lines @@
   DrawProperties<LayerImpl> draw_properties_;
 
   scoped_refptr<base::debug::ConvertableToTraceFormat> debug_info_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_