make StackingClient dispatch to either ash or desktop

ash/shell.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 ASH_SHELL_H_
 #define ASH_SHELL_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 13 matching lines @@
 #include "ui/gfx/size.h"
 
 class CommandLine;
 
 namespace aura {
 class EventFilter;
 class FocusManager;
 class RootWindow;
 class Window;
 namespace client {
+class StackingClient;
 class UserActionClient;
 }
 namespace shared {
 class CompoundEventFilter;
 class InputMethodEventFilter;
 }
 }
 namespace chromeos {
 class OutputConfigurator;
 }
@@ skipping 359 matching lines @@
 
 #if defined(OS_CHROMEOS)
   chromeos::OutputConfigurator* output_configurator() {
     return output_configurator_.get();
   }
   internal::OutputConfiguratorAnimation* output_configurator_animation() {
     return output_configurator_animation_.get();
   }
 #endif  // defined(OS_CHROMEOS)
 
+ aura::client::StackingClient* stacking_client();
+
  private:
   FRIEND_TEST_ALL_PREFIXES(ExtendedDesktopTest, TestCursor);
   FRIEND_TEST_ALL_PREFIXES(WindowManagerTest, MouseEventCursors);
   FRIEND_TEST_ALL_PREFIXES(WindowManagerTest, TransformActivate);
   friend class internal::RootWindowController;
 
   typedef std::pair<aura::Window*, gfx::Rect> WindowAndBoundsPair;
 
   explicit Shell(ShellDelegate* delegate);
   virtual ~Shell();
@@ skipping 109 matching lines @@
 
   // For testing only: simulate that a modal window is open
   bool simulate_modal_window_open_for_testing_;
 
   DISALLOW_COPY_AND_ASSIGN(Shell);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELL_H_