BackgroundSyncManager tracks client registrations

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
 //           event.
+// "unregister" - Unregisters the sync registration from within the sync event.
 
 'use strict';
 
 var resolveCallback = null;
 var rejectCallback = null;
 
 this.onmessage = function(event) {
   if (event.data === 'completeDelayedOneShot') {
     if (resolveCallback === null) {
       sendMessageToClients('sync', 'error - resolveCallback is null');
@@ skipping 10 matching lines @@
       sendMessageToClients('sync', 'error - rejectCallback is null');
       return;
     }
 
     rejectCallback();
     sendMessageToClients('sync', 'ok - delay rejected');
   }
 }
 
 this.onsync = function(event) {
+  var eventProperties = [
+    // Extract name from toString result: "[object <Class>]"
+    Object.prototype.toString.call(event).match(/\s([a-zA-Z]+)/)[1],
+    (typeof event.waitUntil)
+  ];
+
+  if (eventProperties[0] != 'SyncEvent') {
+    sendMessageToClients('sync', 'error - wrong event type');
+    return;
+  }
+
+  if (eventProperties[1] != 'function') {
+    sendMessageToClients('sync', 'error - wrong wait until type');
+  }
+
   if (event.registration === undefined) {
     sendMessageToClients('sync', 'error - event missing registration');
     return;
   }
 
   if (event.registration.tag === undefined) {
     sendMessageToClients('sync', 'error - registration missing tag');
     return;
   }
 
   var tag = event.registration.tag;
 
   if (tag === 'delay') {
     var syncPromise = new Promise(function(resolve, reject) {
       resolveCallback = resolve;
       rejectCallback = reject;
     });
     event.waitUntil(syncPromise);
     return;
   }
 
+  if (tag === 'unregister') {
+    event.waitUntil(event.registration.unregister()
+      .then(function() {
+        sendMessageToClients('sync', 'ok - unregister completed');
+      }));
+    return;
+  }
+
   sendMessageToClients('sync', tag + ' fired');
 };
 
 function sendMessageToClients(type, data) {
   clients.matchAll().then(function(clients) {
     clients.forEach(function(client) {
       client.postMessage({type, data});
     });
   }, function(error) {
     console.log(error);
   });
 }