Remove dispatcher when shutting down RootWindowController

ash/host/ash_window_tree_host_x11.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_X11_H_
 #define ASH_HOST_ASH_WINDOW_TREE_HOST_X11_H_
 
 #include "ash/ash_export.h"
 #include "ash/host/ash_window_tree_host.h"
 #include "ash/host/transformer_helper.h"
@@ skipping 15 matching lines @@
  private:
   // AshWindowTreeHost:
   virtual void ToggleFullScreen() OVERRIDE;
   virtual bool ConfineCursorToRootWindow() OVERRIDE;
   virtual void UnConfineCursor() OVERRIDE;
   virtual void SetRootWindowTransformer(
       scoped_ptr<RootWindowTransformer> transformer) OVERRIDE;
   virtual gfx::Insets GetHostInsets() const OVERRIDE;
   virtual aura::WindowTreeHost* AsWindowTreeHost() OVERRIDE;
   virtual void UpdateDisplayID(int64 id1, int64 id2) OVERRIDE;
+  virtual void PrepareForShutdown() OVERRIDE;
 
   // aura::WindowTreehost:
   virtual void SetBounds(const gfx::Rect& bounds) OVERRIDE;
   virtual gfx::Transform GetRootTransform() const OVERRIDE;
   virtual void SetRootTransform(const gfx::Transform& transform) OVERRIDE;
   virtual gfx::Transform GetInverseRootTransform() const OVERRIDE;
   virtual void UpdateRootWindowSize(const gfx::Size& host_size) OVERRIDE;
   virtual void OnCursorVisibilityChangedNative(bool show) OVERRIDE;
 
   // aura::WindowTreeHostX11:
@@ skipping 20 matching lines @@
   // In mirror mode dual monitors case, the root window is associated with
   // both displays.
   std::pair<int64, int64> display_ids_;
 
   DISALLOW_COPY_AND_ASSIGN(AshWindowTreeHostX11);
 };
 
 }  // namespace ash
 
 #endif  // ASH_HOST_ASH_WINDOW_TREE_HOST_X11_H_