Get rid of the ability to unregister preferences.

chrome/browser/prefs/pref_service_syncable.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 CHROME_BROWSER_PREFS_PREF_SERVICE_SYNCABLE_H_
 #define CHROME_BROWSER_PREFS_PREF_SERVICE_SYNCABLE_H_
 
 #include "base/prefs/pref_service.h"
 #include "chrome/browser/prefs/pref_model_associator.h"
 
@@ skipping 54 matching lines @@
   // syncer::SyncableService directly.
   syncer::SyncableService* GetSyncableService();
 
   // Do not call this after having derived an incognito or per tab pref service.
   virtual void UpdateCommandLinePrefStore(PrefStore* cmd_line_store) OVERRIDE;
 
  private:
   friend class PrefModelAssociator;
 
   void AddRegisteredSyncablePreference(const char* path);
-  virtual void RemoveRegisteredPreference(const char* path) OVERRIDE;
 
   // Invoked internally when the IsSyncing() state changes.
   void OnIsSyncingChanged();
 
   // Whether CreateIncognitoPrefService() has been called to create a
   // "forked" PrefService.
   bool pref_service_forked_;
 
   PrefModelAssociator pref_sync_associator_;
 
   ObserverList<PrefServiceSyncableObserver> observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefServiceSyncable);
 };
 
 #endif  // CHROME_BROWSER_PREFS_PREF_SERVICE_SYNCABLE_H_