Replace more ObserverList with base::ObserverList.

ui/wm/core/transient_window_manager.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 UI_WM_CORE_TRANSIENT_WINDOW_MANAGER_H_
 #define UI_WM_CORE_TRANSIENT_WINDOW_MANAGER_H_
 
 #include <vector>
 
 #include "base/observer_list.h"
@@ skipping 80 matching lines @@
   Windows transient_children_;
 
   // If non-null we're actively restacking transient as the result of a
   // transient ancestor changing.
   aura::Window* stacking_target_;
 
   bool parent_controls_visibility_;
   bool show_on_parent_visible_;
   bool ignore_visibility_changed_event_;
 
-  ObserverList<TransientWindowObserver> observers_;
+  base::ObserverList<TransientWindowObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(TransientWindowManager);
 };
 
 }  // namespace wm
 
 #endif  // UI_WM_CORE_TRANSIENT_WINDOW_MANAGER_H_