Require an explicit ServiceName annotation for interfaces in C++.

mojo/services/notifications/interfaces/notifications.mojom

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [DartPackage="mojo_services"]
 module notifications;
 
 struct NotificationData {
   // Title to be displayed along with the notification, if supported.
   string? title;
@@ skipping 16 matching lines @@
 
 interface Notification {
   // Updates the notification with the information specified in
   // |notification_data|.
   Update(NotificationData notification_data);
 
   // Cancels the notification.
   Cancel();
 };
 
+[ServiceName="notifications::NotificationService"]
 interface NotificationService {
   // Posts a new notification with the information specified in
   // |notification_data| and with any interactions with the notification being
   // communicated to |client|.  |notification| can be used to modify or cancel
   // the notification.
   Post(NotificationData notification_data, NotificationClient? client,
        Notification&? notification);
 };