components: Move PrefRegistrySyncable into user_prefs namespace.

chrome/browser/prefs/browser_prefs.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_BROWSER_PREFS_H_
 #define CHROME_BROWSER_PREFS_BROWSER_PREFS_H_
 
 class PrefRegistrySimple;
-class PrefRegistrySyncable;
 class PrefService;
 class Profile;
 
+namespace user_prefs {
+class PrefRegistrySyncable;
+}
+
 namespace chrome {
 
 // Register all prefs that will be used via the local state PrefService.
 void RegisterLocalState(PrefRegistrySimple* registry);
 
 // Register all prefs that will be used via a PrefService attached to a Profile.
-void RegisterUserPrefs(PrefRegistrySyncable* registry);
+void RegisterUserPrefs(user_prefs::PrefRegistrySyncable* registry);
 
 // Migrates prefs from |local_state| to |profile|'s pref store.
 void MigrateBrowserPrefs(Profile* profile, PrefService* local_state);
 
 // Migrates prefs in |profile|'s pref store.
 void MigrateUserPrefs(Profile* profile);
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_PREFS_BROWSER_PREFS_H_