Clean up old legacy preference migration logic.

chrome/browser/prefs/chrome_pref_service_factory.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_CHROME_PREF_SERVICE_FACTORY_H_
 #define CHROME_BROWSER_PREFS_CHROME_PREF_SERVICE_FACTORY_H_
 
 #include <memory>
 
 #include "base/memory/ref_counted.h"
@@ skipping 82 matching lines @@
     const base::DictionaryValue& master_prefs);
 
 // Retrieves the time of the last preference reset event, if any, for the
 // provided profile. If no reset has occurred, returns a null |Time|.
 base::Time GetResetTime(Profile* profile);
 
 // Clears the time of the last preference reset event, if any, for the provided
 // profile.
 void ClearResetTime(Profile* profile);
 
-// Register local state prefs used by chrome preference system.
-void RegisterPrefs(PrefRegistrySimple* registry);
-
 // Register user prefs used by chrome preference system.
 void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
 }  // namespace chrome_prefs
 
 #endif  // CHROME_BROWSER_PREFS_CHROME_PREF_SERVICE_FACTORY_H_