Use ARC_APPLICATION notifier-type for ARC notifications

Bug: 782005
Change-Id: Icd1888daf9873719bce2b4d37d7d66e31c24da66
Reviewed-on: https://chromium-review.googlesource.com/763031Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Commit-Queue: Yoshiki Iguchi <yoshiki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#515886}

ui/arc/notification/arc_notification_item_impl.cc

@@ -91,7 +91,7 @@ void ArcNotificationItemImpl::OnUpdatedFromAndroid(
   }
 
   message_center::NotifierId notifier_id(
-      message_center::NotifierId::SYSTEM_COMPONENT, kNotifierId);
+      message_center::NotifierId::ARC_APPLICATION, kNotifierId);
   notifier_id.profile_id = profile_id_.GetUserEmail();
 
   auto notification = std::make_unique<message_center::Notification>(