Draft change to use base::Closure instead of PrefObserver in PrefChangeRegistrar.

base/prefs/public/pref_service_base.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.
 
 // This is the base interface for a preference services that provides
 // a way to access the application's current preferences.
 //
 // This base interface assumes all preferences are local.  See
 // SyncablePrefServiceBase for the interface to a preference service
 // that stores preferences that can be synced.
 //
 // Chromium settings and storage represent user-selected preferences and
 // information and MUST not be extracted, overwritten or modified except
 // through Chromium defined APIs.
 
 #ifndef BASE_PREFS_PUBLIC_PREF_SERVICE_BASE_H_
 #define BASE_PREFS_PUBLIC_PREF_SERVICE_BASE_H_
 
+#include "base/callback_forward.h"
 #include "base/values.h"
 
 namespace content {
 class BrowserContext;
 }
 
 namespace subtle {
 class PrefMemberBase;
 }
 
@@ skipping 223 matching lines @@
   // access to the otherwise protected members Add/RemovePrefObserver.
   // PrefMember registers for preferences changes notification directly to
   // avoid the storage overhead of the registrar, so its base class must be
   // declared as a friend, too.
   friend class PrefChangeRegistrar;
   friend class subtle::PrefMemberBase;
 
   // These are protected so they can only be accessed by the friend
   // classes listed above.
   //
-  // If the pref at the given path changes, we call the observer's
-  // OnPreferenceChanged method. Note that observers should not call
-  // these methods directly but rather use a PrefChangeRegistrar to
-  // make sure the observer gets cleaned up properly.
-  virtual void AddPrefObserver(const char* path, PrefObserver* obs) = 0;
-  virtual void RemovePrefObserver(const char* path, PrefObserver* obs) = 0;
+  // If the pref at the given path changes, we run the closure. Note
+  // that observers should not call these methods directly but rather
+  // use a PrefChangeRegistrar to make sure the observer gets cleaned
+  // up properly.
+  virtual void AddPrefObserver(const char* path, const base::Closure& obs) = 0;
+  virtual void RemovePrefObserver(const char* path,
+                                  const base::Closure& obs) = 0;
 };
 
 #endif  // BASE_PREFS_PUBLIC_PREF_SERVICE_BASE_H_