arc: Show custom notification via notification surface

ui/arc/notification/arc_notification_manager.cc

Index: ui/arc/notification/arc_notification_manager.cc
diff --git a/ui/arc/notification/arc_notification_manager.cc b/ui/arc/notification/arc_notification_manager.cc
index b27e2c563746f09a2afb0398b278a4869fbe0843..cd2de734b2e467609a6684a7b7959dc2b6b7842e 100644
--- a/ui/arc/notification/arc_notification_manager.cc
+++ b/ui/arc/notification/arc_notification_manager.cc
@@ -9,6 +9,7 @@
 #include "base/memory/ptr_util.h"
 #include "base/stl_util.h"
 #include "ui/arc/notification/arc_notification_item.h"
+#include "ui/arc/notification/arc_notification_surface_collection.h"
 
 namespace arc {
 
@@ -25,6 +26,7 @@ ArcNotificationManager::ArcNotificationManager(
     : ArcService(bridge_service),
       main_profile_id_(main_profile_id),
       message_center_(message_center),
+      notification_surface_collection_(new ArcNotificationSurfaceCollection),
       binding_(this) {
   arc_bridge_service()->AddObserver(this);
 }