Split PrefService into PrefService, PrefServiceSimple and PrefServiceSyncable.

chrome/browser/metrics/metrics_service.h

Index: chrome/browser/metrics/metrics_service.h
diff --git a/chrome/browser/metrics/metrics_service.h b/chrome/browser/metrics/metrics_service.h
index d95d3314ba3268b6b3c1d1d68aa396705fd4403b..308fe57ba1db9653251effc95e3bf085f6b34f16 100644
--- a/chrome/browser/metrics/metrics_service.h
+++ b/chrome/browser/metrics/metrics_service.h
@@ -34,6 +34,7 @@ class BookmarkModel;
 class BookmarkNode;
 class MetricsReportingScheduler;
 class PrefService;
+class PrefServiceSimple;
 class Profile;
 class TemplateURLService;
 
@@ -123,7 +124,7 @@ class MetricsService
 
   // At startup, prefs needs to be called with a list of all the pref names and
   // types we'll be using.
-  static void RegisterPrefs(PrefService* local_state);
+  static void RegisterPrefs(PrefServiceSimple* local_state);
 
   // Set up notifications which indicate that a user is performing work. This is
   // useful to allow some features to sleep, until the machine becomes active,