Remove PrepareForShutdown

ash/root_window_settings.h

 // Copyright 2013 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_ROOT_WINDOW_SETTINGS_H_
 #define ASH_ROOT_WINDOW_SETTINGS_H_
 
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 
@@ skipping 11 matching lines @@
 // it can prevent mis-using on non root window.
 struct RootWindowSettings {
   RootWindowSettings();
 
   // ID of the display associated with the root window.
   int64 display_id;
 
   // RootWindowController for the root window. This may be NULL
   // for the root window used for mirroring.
   RootWindowController* controller;
+
+  // True if the root window has already been shutdown.
+  bool shutdown;
 };
 
 // Initializes and returns RootWindowSettings for |root|.
 // It is owned by the |root|.
 RootWindowSettings* InitRootWindowSettings(aura::Window* root);
 
 // Returns the RootWindowSettings for |root|.
 ASH_EXPORT RootWindowSettings* GetRootWindowSettings(aura::Window* root);
 
 // const version of GetRootWindowSettings.
 ASH_EXPORT const RootWindowSettings*
 GetRootWindowSettings(const aura::Window* root);
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_ROOT_WINDOW_SETTINGS_H_