Add OnDisplayMetricsChanged in DisplayObserver.

ash/shell/window_watcher.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_WINDOW_WATCHER_H_
 #define ASH_SHELL_WINDOW_WATCHER_H_
 
 #include <map>
 
 #include "ash/shelf/shelf_item_types.h"
@@ skipping 20 matching lines @@
   WindowWatcher();
   virtual ~WindowWatcher();
 
   aura::Window* GetWindowByID(ash::ShelfID id);
 
   // aura::WindowObserver overrides:
   virtual void OnWindowAdded(aura::Window* new_window) OVERRIDE;
   virtual void OnWillRemoveWindow(aura::Window* window) OVERRIDE;
 
   // gfx::DisplayObserver overrides:
-  virtual void OnDisplayBoundsChanged(const gfx::Display& display) OVERRIDE;
   virtual void OnDisplayAdded(const gfx::Display& new_display) OVERRIDE;
   virtual void OnDisplayRemoved(const gfx::Display& old_display) OVERRIDE;
+  virtual void OnDisplayMetricsChanged(const gfx::Display& display,
+                                       uint32_t metrics) OVERRIDE;
 
  private:
   class WorkspaceWindowWatcher;
 
   typedef std::map<ash::ShelfID, aura::Window*> IDToWindow;
 
   // Maps from window to the id we gave it.
   IDToWindow id_to_window_;
 
   scoped_ptr<WorkspaceWindowWatcher> workspace_window_watcher_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowWatcher);
 };
 
 }  // namespace shell
 }  // namespace ash
 
 #endif  // ASH_SHELL_WINDOW_WATCHER_H_