Use WebKit compositor in ui::Layer

ui/gfx/compositor/compositor.h

 // Copyright (c) 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 UI_GFX_COMPOSITOR_COMPOSITOR_H_
 #define UI_GFX_COMPOSITOR_COMPOSITOR_H_
 #pragma once
 
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
@@ skipping 89 matching lines @@
                             gfx::AcceleratedWidget widget,
                             const gfx::Size& size);
 
   // Creates a new texture. The caller owns the returned object.
   virtual Texture* CreateTexture() = 0;
 
   // Blurs the specific region in the compositor.
   virtual void Blur(const gfx::Rect& bounds) = 0;
 
   // Schedules a redraw of the layer tree associated with this compositor.
-  void ScheduleDraw() {
-    delegate_->ScheduleDraw();
-  }
+  virtual void ScheduleDraw();
 
   // Sets the root of the layer tree drawn by this Compositor.
   // The Compositor does not own the root layer.
   Layer* root_layer() { return root_layer_; }
   void SetRootLayer(Layer* root_layer);
 
   // Draws the scene created by the layer tree and any visual effects. If
   // |force_clear| is true, this will cause the compositor to clear before
   // compositing.
   void Draw(bool force_clear);
@@ skipping 20 matching lines @@
   Compositor(CompositorDelegate* delegate, const gfx::Size& size);
   virtual ~Compositor();
 
   // Notifies the compositor that compositing is about to start.
   virtual void OnNotifyStart(bool clear) = 0;
 
   // Notifies the compositor that compositing is complete.
   virtual void OnNotifyEnd() = 0;
 
   virtual void OnWidgetSizeChanged() = 0;
+  virtual void OnRootLayerChanged();
+  virtual void DrawTree();
 
   CompositorDelegate* delegate() { return delegate_; }
 
  private:
   // Notifies the compositor that compositing is about to start. See Draw() for
   // notes about |force_clear|.
   void NotifyStart(bool force_clear);
 
   // Notifies the compositor that compositing is complete.
   void NotifyEnd();
 
   CompositorDelegate* delegate_;
   gfx::Size size_;
 
   // The root of the Layer tree drawn by this compositor.
   Layer* root_layer_;
 
   ObserverList<CompositorObserver> observer_list_;
 
   friend class base::RefCounted<Compositor>;
 };
 
 }  // namespace ui
 
 #endif  // UI_GFX_COMPOSITOR_COMPOSITOR_H_