components: Move PrefRegistrySyncable into user_prefs namespace.

chrome/browser/signin/signin_manager_factory.h

Index: chrome/browser/signin/signin_manager_factory.h
diff --git a/chrome/browser/signin/signin_manager_factory.h b/chrome/browser/signin/signin_manager_factory.h
index c62a8d61c5306eedc6b651c8d9bc5658b4254c9b..d10df60b05843e76288d12bcf4cc321c22d2efd3 100644
--- a/chrome/browser/signin/signin_manager_factory.h
+++ b/chrome/browser/signin/signin_manager_factory.h
@@ -11,7 +11,6 @@
 class SigninManager;
 class SigninManagerBase;
 class PrefRegistrySimple;
-class PrefRegistrySyncable;
 class Profile;
 
 // Singleton that owns all SigninManagers and associates them with
@@ -41,7 +40,8 @@ class SigninManagerFactory : public ProfileKeyedServiceFactory {
   static SigninManagerFactory* GetInstance();
 
   // Implementation of ProfileKeyedServiceFactory (public so tests can call it).
-  virtual void RegisterUserPrefs(PrefRegistrySyncable* registry) OVERRIDE;
+  virtual void RegisterUserPrefs(
+      user_prefs::PrefRegistrySyncable* registry) OVERRIDE;
 
   // Registers the browser-global prefs used by SigninManager.
   static void RegisterPrefs(PrefRegistrySimple* registry);