Unified Desktop: hook up ash to allow unified desktop mode

ash/host/ash_window_tree_host.h

 // Copyright 2014 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_HOST_ASH_WINDOW_TREE_HOST_H_
 #define ASH_HOST_ASH_WINDOW_TREE_HOST_H_
 
 #include "ash/ash_export.h"
 #include "base/memory/scoped_ptr.h"
 
@@ skipping 37 matching lines @@
   virtual void SetRootWindowTransformer(
       scoped_ptr<RootWindowTransformer> transformer) = 0;
 
   virtual gfx::Insets GetHostInsets() const = 0;
 
   virtual aura::WindowTreeHost* AsWindowTreeHost() = 0;
 
   // Stop listening for events in preparation for shutdown.
   virtual void PrepareForShutdown() {}
 
+  virtual void RegisterMirroringHost(AshWindowTreeHost* mirroring_ash_host) {}
+
  protected:
   // Translates the native mouse location into screen coordinates.
   void TranslateLocatedEvent(ui::LocatedEvent* event);
 };
 
 }  // namespace ash
 
 #endif  // ASH_HOST_ASH_WINDOW_TREE_HOST_H_