Replace more ObserverList with base::ObserverList.

ash/system/chromeos/power/power_status.h

 // Copyright (c) 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_SYSTEM_CHROMEOS_POWER_POWER_STATUS_H_
 #define ASH_SYSTEM_CHROMEOS_POWER_POWER_STATUS_H_
 
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "base/observer_list.h"
@@ skipping 121 matching lines @@
   void SetProtoForTesting(const power_manager::PowerSupplyProperties& proto);
 
  protected:
   PowerStatus();
   ~PowerStatus() override;
 
  private:
   // Overriden from PowerManagerClient::Observer.
   void PowerChanged(const power_manager::PowerSupplyProperties& proto) override;
 
-  ObserverList<Observer> observers_;
+  base::ObserverList<Observer> observers_;
 
   // Current state.
   power_manager::PowerSupplyProperties proto_;
 
   DISALLOW_COPY_AND_ASSIGN(PowerStatus);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_POWER_POWER_STATUS_H_