[Sync] Make P2PNotifier emit a notification only if some enabled types changed

sync/notifier/p2p_notifier.cc

Index: sync/notifier/p2p_notifier.cc
diff --git a/sync/notifier/p2p_notifier.cc b/sync/notifier/p2p_notifier.cc
index e2a4209bfdd3b8bd0d363df1978a36cf97b97e36..c4fcfbe649eab9dd939630969d76165031d42984 100644
--- a/sync/notifier/p2p_notifier.cc
+++ b/sync/notifier/p2p_notifier.cc
@@ -260,13 +260,14 @@ void P2PNotifier::OnIncomingNotification(
              << "not emitting notification";
     return;
   }
-  if (notification_data.GetChangedTypes().Empty()) {
-    DVLOG(1) << "No changed types -- not emitting notification";
+  const ModelTypeSet types_to_notify =
+      Intersection(enabled_types_, notification_data.GetChangedTypes());
+  if (types_to_notify.Empty()) {
+    DVLOG(1) << "No enabled and changed types -- not emitting notification";
     return;
   }
   const ModelTypePayloadMap& type_payloads =
-      ModelTypePayloadMapFromEnumSet(
-          notification_data.GetChangedTypes(), std::string());
+      ModelTypePayloadMapFromEnumSet(types_to_notify, std::string());
   FOR_EACH_OBSERVER(SyncNotifierObserver, observer_list_,
                     OnIncomingNotification(type_payloads, REMOTE_NOTIFICATION));
 }