Unified Desktop: hook up ash to allow unified desktop mode

ash/host/ash_window_tree_host_init_params.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_WINDOW_TREE_HOST_INIT_PARAMS_H_
 #define ASH_HOST_WINDOW_TREE_HOST_INIT_PARAMS_H_
 
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
 #include "ash/ash_export.h"
 #include "ui/gfx/geometry/rect.h"
 
 namespace ash {
 
 struct ASH_EXPORT AshWindowTreeHostInitParams {
   AshWindowTreeHostInitParams();
   ~AshWindowTreeHostInitParams();
 
   gfx::Rect initial_bounds;
 
+  bool offscreen;
+
 #if defined(OS_WIN)
   HWND remote_hwnd;
 #endif
 };
 
 }  // namespace ash
 
 #endif  // ASH_HOST_WINDOW_TREE_HOST_INIT_PARAMS_H_