[BackgroundSync] Only allow SyncManager.register to occur from main frame

content/test/data/background_sync/service_worker.js

 // 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.
 
 // The "onsync" event currently understands commands (passed as
 // registration tags) coming from the test. Any other tag is
 // passed through to the document unchanged.
 //
 // "delay" - Delays finishing the sync event with event.waitUntil.
 //           Send a postMessage of "completeDelayedOneShot" to finish the
@@ skipping 87 matching lines @@
       rejectCallback = reject;
     });
     event.waitUntil(syncPromise);
     return;
   }
 
   sendMessageToClients('sync', tag + ' fired');
 };
 
 function sendMessageToClients(type, data) {
-  clients.matchAll().then(function(clients) {
+  clients.matchAll({ includeUncontrolled: true }).then(function(clients) {
     clients.forEach(function(client) {
       client.postMessage({type, data});
     });
   }, function(error) {
     console.log(error);
   });
 }
 
 function sendSyncErrorToClients(error) {
   sendMessageToClients('sync', error.name + ' - ' + error.message);
 }