Replace more ObserverList with base::ObserverList.

ash/shell.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_H_
 #define ASH_SHELL_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 739 matching lines @@
   AshNativeCursorManager* native_cursor_manager_;
 
 // Cursor may be hidden on certain key events in ChromeOS, whereas we never hide
 // the cursor on Windows.
 #if defined(OS_CHROMEOS)
   CursorManager cursor_manager_;
 #else  // !defined(OS_CHROMEOS)
   ::wm::CursorManager cursor_manager_;
 #endif  // defined(OS_CHROMEOS)
 
-  ObserverList<ShellObserver> observers_;
+  base::ObserverList<ShellObserver> observers_;
 
   // For testing only: simulate that a modal window is open
   bool simulate_modal_window_open_for_testing_;
 
   bool is_touch_hud_projection_enabled_;
 
   // Injected content::GPUDataManager support.
   scoped_ptr<GPUSupport> gpu_support_;
 
   DISALLOW_COPY_AND_ASSIGN(Shell);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELL_H_