Mojo C++ bindings: support enum validation.

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 694f41bdde7867f0f7218a3c1484f85e7bc4c4a8..5be5ac144fb4a99d18c08b5d2e74d46d849b1e26 100644
--- a/ui/arc/notification/arc_notification_item.cc
+++ b/ui/arc/notification/arc_notification_item.cc
@@ -122,8 +122,8 @@ void ArcNotificationItem::UpdateWithArcNotificationData(
                                data.progress_max * 100))));
       break;
   }
-  DCHECK(ArcNotificationType_IsValidValue(data.type))
-      << "Unsupported notification type: " << data.type;
+  DCHECK(IsKnownEnumValue(data.type)) << "Unsupported notification type: "
+                                      << data.type;
 
   // The identifier of the notifier, which is used to distinguish the notifiers
   // in the message center.