compositor: Reuse GetXDisplay() function from x11_util.h

ui/compositor/test/test_compositor_host.h

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// 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 UI_COMPOSITOR_TEST_TEST_COMPOSITOR_HOST_H_
 #define UI_COMPOSITOR_TEST_TEST_COMPOSITOR_HOST_H_
 
-#include "base/message_loop.h"
-
 namespace gfx {
 class Rect;
 }
 
 namespace ui {
 
 class Compositor;
 
 class TestCompositorHost {
  public:
   virtual ~TestCompositorHost() {}
 
   // Creates a new TestCompositorHost. The caller owns the returned value.
   static TestCompositorHost* Create(const gfx::Rect& bounds);
 
   // Shows the TestCompositorHost.
   virtual void Show() = 0;
 
-  virtual ui::Compositor* GetCompositor() = 0;
+  virtual Compositor* GetCompositor() = 0;
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_TEST_TEST_COMPOSITOR_HOST_H_