Move base/prefs to components/prefs

base/prefs/pref_observer.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 BASE_PREFS_PREF_OBSERVER_H_
-#define BASE_PREFS_PREF_OBSERVER_H_
-
-#include <string>
-
-class PrefService;
-
-// Used internally to the Prefs subsystem to pass preference change
-// notifications between PrefService, PrefNotifierImpl and
-// PrefChangeRegistrar.
-class PrefObserver {
- public:
-  virtual void OnPreferenceChanged(PrefService* service,
-                                   const std::string& pref_name) = 0;
-};
-
-#endif  // BASE_PREFS_PREF_OBSERVER_H_
+// TODO(brettw) remove this forwarding header when prefs is completely moved to
+// components.
+#include "components/prefs/pref_observer.h"