Split PrefService into PrefService, PrefServiceSimple and PrefServiceSyncable.

chrome/browser/chromeos/login/user_manager.h

Index: chrome/browser/chromeos/login/user_manager.h
diff --git a/chrome/browser/chromeos/login/user_manager.h b/chrome/browser/chromeos/login/user_manager.h
index a869380a7b60943b18457cc1ce9c04ff830c5a10..ee2b59a098681d7128cfbc8fca1ac58815ef5983 100644
--- a/chrome/browser/chromeos/login/user_manager.h
+++ b/chrome/browser/chromeos/login/user_manager.h
@@ -10,7 +10,7 @@
 #include "base/memory/singleton.h"
 #include "chrome/browser/chromeos/login/user.h"
 
-class PrefService;
+class PrefServiceSimple;
 
 namespace chromeos {
 
@@ -60,7 +60,7 @@ class UserManager {
   static UserManager* Set(UserManager* mock);
 
   // Registers user manager preferences.
-  static void RegisterPrefs(PrefService* local_state);
+  static void RegisterPrefs(PrefServiceSimple* local_state);
 
   // Indicates imminent shutdown, allowing the UserManager to remove any
   // observers it has registered.