Use constexpr TaskTraits constructor in ui.

ui/arc/notification/arc_notification_item.cc

Index: ui/arc/notification/arc_notification_item.cc
diff --git a/ui/arc/notification/arc_notification_item.cc b/ui/arc/notification/arc_notification_item.cc
index cc44abbcc22b74c1b570333c58176ad2fe02d6e8..2c4cac44b5317b355a1796d20a505bae1f2a5dd9 100644
--- a/ui/arc/notification/arc_notification_item.cc
+++ b/ui/arc/notification/arc_notification_item.cc
@@ -236,8 +236,7 @@ void ArcNotificationItem::UpdateWithArcNotificationData(
 
   // TODO(yoshiki): Remove decoding by passing a bitmap directly from Android.
   base::PostTaskWithTraitsAndReplyWithResult(
-      FROM_HERE, base::TaskTraits().WithShutdownBehavior(
-                     base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN),
+      FROM_HERE, {base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN},
       base::Bind(&DecodeImage, data->icon_data),
       base::Bind(&ArcNotificationItem::OnImageDecoded,
                  weak_ptr_factory_.GetWeakPtr()));