make StackingClient dispatch to either ash or desktop

chrome/browser/ui/aura/chrome_browser_main_extra_parts_aura.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 CHROME_BROWSER_UI_AURA_CHROME_BROWSER_MAIN_EXTRA_PARTS_AURA_H_
 #define CHROME_BROWSER_UI_AURA_CHROME_BROWSER_MAIN_EXTRA_PARTS_AURA_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/chrome_browser_main_extra_parts.h"
 
 namespace aura {
-class DesktopStackingClient;
+namespace client {
+class StackingClient;
+}
 }
 
 class ChromeBrowserMainExtraPartsAura : public ChromeBrowserMainExtraParts {
  public:
   ChromeBrowserMainExtraPartsAura();
   virtual ~ChromeBrowserMainExtraPartsAura();
 
   // Overridden from ChromeBrowserMainExtraParts:
   virtual void PreProfileInit() OVERRIDE;
   virtual void PostMainMessageLoopRun() OVERRIDE;
 
  private:
-  scoped_ptr<aura::DesktopStackingClient> stacking_client_;
+  scoped_ptr<aura::client::StackingClient> stacking_client_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeBrowserMainExtraPartsAura);
 };
 
 #endif  // CHROME_BROWSER_UI_AURA_CHROME_BROWSER_MAIN_EXTRA_PARTS_AURA_H_