Add IPC messages for ARC notification

components/arc/arc_bridge_service.cc

Index: components/arc/arc_bridge_service.cc
diff --git a/components/arc/arc_bridge_service.cc b/components/arc/arc_bridge_service.cc
index af2835d87e8d73344624d829a6457e09c3d71f15..ef2c0eed130f90bae8a1b337db01442a8da267ee 100644
--- a/components/arc/arc_bridge_service.cc
+++ b/components/arc/arc_bridge_service.cc
@@ -57,6 +57,17 @@ void ArcBridgeService::RemoveObserver(Observer* observer) {
   observer_list_.RemoveObserver(observer);
 }
 
+void ArcBridgeService::AddNotificationObserver(NotificationObserver* observer) {
+  DCHECK(origin_task_runner()->RunsTasksOnCurrentThread());
+  notification_observer_list_.AddObserver(observer);
+}
+
+void ArcBridgeService::RemoveNotificationObserver(
+    NotificationObserver* observer) {
+  DCHECK(origin_task_runner()->RunsTasksOnCurrentThread());
+  notification_observer_list_.RemoveObserver(observer);
+}
+
 void ArcBridgeService::SetState(State state) {
   DCHECK(origin_task_runner()->RunsTasksOnCurrentThread());
   // DCHECK on enum classes not supported.