Make SyncBackendRegistrar aware of loaded data

sync/internal_api/js_sync_manager_observer.cc

Index: sync/internal_api/js_sync_manager_observer.cc
diff --git a/sync/internal_api/js_sync_manager_observer.cc b/sync/internal_api/js_sync_manager_observer.cc
index 5eda7f113c55b3ff47fd0d27c963740b4688febd..078e1e9a51d32d72dc496ba44cea6f36a4f4b4b0 100644
--- a/sync/internal_api/js_sync_manager_observer.cc
+++ b/sync/internal_api/js_sync_manager_observer.cc
@@ -124,13 +124,17 @@ void JsSyncManagerObserver::OnActionableError(
 
 void JsSyncManagerObserver::OnInitializationComplete(
     const WeakHandle<JsBackend>& js_backend,
-    bool success) {
+    bool success, syncer::ModelTypeSet restored_types) {
   if (!event_handler_.IsInitialized()) {
     return;
   }
   // Ignore the |js_backend| argument; it's not really convertible to
   // JSON anyway.
-  HandleJsEvent(FROM_HERE, "onInitializationComplete", JsEventDetails());
+
+  DictionaryValue* details = new DictionaryValue();
+  details->Set("restoredTypes", ModelTypeSetToValue(restored_types));
+
+  HandleJsEvent(FROM_HERE, "onInitializationComplete", JsEventDetails(details));
 }
 
 void JsSyncManagerObserver::OnStopSyncingPermanently() {