Replace more ObserverList with base::ObserverList.

ui/display/chromeos/x11/native_display_delegate_x11.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_DISPLAY_CHROMEOS_X11_NATIVE_DISPLAY_DELEGATE_X11_H_
 #define UI_DISPLAY_CHROMEOS_X11_NATIVE_DISPLAY_DELEGATE_X11_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 144 matching lines @@
   // propagate them.
   ScopedVector<DisplaySnapshot> cached_outputs_;
 
   scoped_ptr<HelperDelegate> helper_delegate_;
 
   // Processes X11 display events associated with the root window and notifies
   // |observers_| when a display change has occurred.
   scoped_ptr<NativeDisplayEventDispatcherX11> platform_event_dispatcher_;
 
   // List of observers waiting for display configuration change events.
-  ObserverList<NativeDisplayObserver> observers_;
+  base::ObserverList<NativeDisplayObserver> observers_;
 
   // A background color used during boot time + multi displays.
   uint32_t background_color_argb_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeDisplayDelegateX11);
 };
 
 }  // namespace ui
 
 #endif  // UI_DISPLAY_CHROMEOS_X11_NATIVE_DISPLAY_DELEGATE_X11_H_