Route Scroll events through a cc::InputHandler

ui/compositor/layer.h

 // Copyright (c) 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 UI_COMPOSITOR_LAYER_H_
 #define UI_COMPOSITOR_LAYER_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 337 matching lines @@
   // delegated frame.
   void OnDelegatedFrameDamage(const gfx::Rect& damage_rect_in_dip);
 
   // Requets a copy of the layer's output as a texture or bitmap.
   void RequestCopyOfOutput(std::unique_ptr<cc::CopyOutputRequest> request);
 
   // Makes this Layer scrollable, clipping to |parent_clip_layer|. |on_scroll|
   // is invoked when scrolling performed by the cc::InputHandler is committed.
   void SetScrollable(Layer* parent_clip_layer, const base::Closure& on_scroll);
 
+  // Gets the ElementId. For a ui::Layer, this has primaryId equal to the
+  // LayerImpl's id() and a secondaryId of 0.
+  cc::ElementId GetElementId() const;
+
   // Gets and sets the current scroll offset of the layer.
   gfx::ScrollOffset CurrentScrollOffset() const;
   void SetScrollOffset(const gfx::ScrollOffset& offset);
 
   // ContentLayerClient
   gfx::Rect PaintableRegion() override;
   scoped_refptr<cc::DisplayItemList> PaintContentsToDisplayList(
       ContentLayerClient::PaintingControlSetting painting_control) override;
   bool FillsBoundsCompletely() const override;
   size_t GetApproximateUnsharedMemoryUsage() const override;
@@ skipping 169 matching lines @@
   // The size of the frame or texture in DIP, set when SetShowDelegatedContent
   // or SetTextureMailbox was called.
   gfx::Size frame_size_in_dip_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_LAYER_H_