chrome: Cleanup class/struct forward declarations

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 10 matching lines @@
 }
 
 namespace sync_preferences {
 class PrefServiceSyncable;
 }
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
-class PrefHashStore;
 class PrefRegistry;
-class PrefRegistrySimple;
 class PrefService;
 
 class PrefStore;
 class Profile;
 class SupervisedUserSettingsService;
 class TrackedPreferenceValidationDelegate;
 
 namespace chrome_prefs {
 
 namespace internals {
@@ skipping 55 matching lines @@
 // Clears the time of the last preference reset event, if any, for the provided
 // profile.
 void ClearResetTime(Profile* profile);
 
 // 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_