Replace more ObserverList with base::ObserverList.

ash/content/display/screen_orientation_controller_chromeos.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_CONTENT_DISPLAY_SCREEN_ORIENTATION_CONTROLLER_CHROMEOS_H_
 #define ASH_CONTENT_DISPLAY_SCREEN_ORIENTATION_CONTROLLER_CHROMEOS_H_
 
 #include <map>
 
 #include "ash/ash_export.h"
@@ skipping 161 matching lines @@
 
   // The rotation of the display set by the user. This rotation will be
   // restored upon exiting maximize mode.
   gfx::Display::Rotation user_rotation_;
 
   // The current rotation set by ScreenOrientationController for the internal
   // display.
   gfx::Display::Rotation current_rotation_;
 
   // Rotation Lock observers.
-  ObserverList<Observer> observers_;
+  base::ObserverList<Observer> observers_;
 
   // Tracks all windows that have requested a lock, as well as the requested
   // orientation.
   std::map<aura::Window*, blink::WebScreenOrientationLockType> locking_windows_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenOrientationController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_CONTENT_DISPLAY_SCREEN_ORIENTATION_CONTROLLER_CHROMEOS_H_