Remove PrefServiceSimple, replacing it with PrefService and PrefRegistrySimple.

chrome/browser/prefs/pref_service_syncable.h

Index: chrome/browser/prefs/pref_service_syncable.h
diff --git a/chrome/browser/prefs/pref_service_syncable.h b/chrome/browser/prefs/pref_service_syncable.h
index c0da1356977e11ef2dfebdcab2397e0ebe92f6f2..0f242e34398548b1fca7ff8b524e2ba2c968424f 100644
--- a/chrome/browser/prefs/pref_service_syncable.h
+++ b/chrome/browser/prefs/pref_service_syncable.h
@@ -33,7 +33,7 @@ class PrefServiceSyncable : public PrefService {
       PrefNotifierImpl* pref_notifier,
       PrefValueStore* pref_value_store,
       PersistentPrefStore* user_prefs,
-      DefaultPrefStore* default_store,
+      PrefRegistry* pref_registry,
       base::Callback<void(PersistentPrefStore::PrefReadError)>
           read_error_callback,
       bool async);
@@ -55,8 +55,6 @@ class PrefServiceSyncable : public PrefService {
   void AddObserver(PrefServiceSyncableObserver* observer);
   void RemoveObserver(PrefServiceSyncableObserver* observer);
 
-  virtual void UnregisterPreference(const char* path) OVERRIDE;
-
   void RegisterBooleanPref(const char* path,
                            bool default_value,
                            PrefSyncStatus sync_status);
@@ -101,6 +99,8 @@ class PrefServiceSyncable : public PrefService {
                           uint64 default_value,
                           PrefSyncStatus sync_status);
 
+  void UnregisterPreference(const char* path);
+
   // TODO(zea): Have PrefServiceSyncable implement
   // syncer::SyncableService directly.
   syncer::SyncableService* GetSyncableService();