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 48d3868857a504464c5a1314d9b62be854e2be6c..e13e4556af374bb643fc80a86786a9b761ab9f7d 100644
--- a/ui/arc/notification/arc_notification_item.cc
+++ b/ui/arc/notification/arc_notification_item.cc
@@ -127,8 +127,8 @@ 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;
 
   for (size_t i = 0; i < data.buttons.size(); i++) {
     rich_data.buttons.push_back(message_center::ButtonInfo(