Use a mocked compositor for unit tests

ui/gfx/compositor/test_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_TEST_COMPOSITOR_H_
 #define UI_GFX_COMPOSITOR_TEST_COMPOSITOR_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/compiler_specific.h"
 #include "ui/gfx/compositor/compositor.h"
 
 namespace ui {
 
 class TestCompositorDelegate;
 
 // Trivial Compositor implementation that creates Textures of type TestTexture.
 class TestCompositor : public ui::Compositor {
  public:
-  TestCompositor();
+  explicit TestCompositor(CompositorDelegate* owner);
   virtual ~TestCompositor();
 
   // ui::Compositor:
   virtual ui::Texture* CreateTexture() OVERRIDE;
   virtual void OnNotifyStart(bool clear) OVERRIDE;
   virtual void OnNotifyEnd() OVERRIDE;
   virtual void Blur(const gfx::Rect& bounds) OVERRIDE;
   virtual void DrawTree() OVERRIDE;
 
+  // A simple factory that creates a test compositor with a given delegate
+  static ui::Compositor* Create(ui::CompositorDelegate* owner);
+
  protected:
   virtual void OnWidgetSizeChanged() OVERRIDE;
 
  private:
   scoped_ptr<TestCompositorDelegate> owned_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(TestCompositor);
 };
 
 }  // namespace ui
 
 #endif  // UI_GFX_COMPOSITOR_TEST_COMPOSITOR_H_