Browser side of ServiceWorker requestSyncEvents() function

content/test/data/service_worker/sync.js

 // Copyright 2014 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.
 
-var code = 404;
+var sawSyncEvent = false;
+var fetchCount = 0;
+
+// onfetch is a state machine:
+// 1st call returns 404 and calls requestSyncEvents()
+// .. sync doesn't fire ..
+// 2nd call returns 404 and calls requestSyncEvents(true)
+// .. sync fires ..
+// 3rd call returns 200 and calls requestSyncEvents(false)
+// .. sync doesn't fire ..
+// 4th call returns 404
 
 this.onfetch = function(event) {
+    var code = sawSyncEvent ? 200 : 404;
     response = new Response({
         statusCode: code,
         statusText: 'OK',
         method: 'GET',
         headers: {
             'Content-Language': 'fi',
             'Content-Type': 'text/html; charset=UTF-8'
         }
     });
 
     event.respondWith(new Promise(function(r) {
         setTimeout(function() { r(response); }, 5);
     }));
+
+    if (fetchCount == 0) {
+        requestSyncEvents();
+    } else if (fetchCount == 1) {
+        requestSyncEvents(true);
+    } else if (fetchCount == 2) {
+        requestSyncEvents(false);
+    }
+
+    fetchCount += 1;
+    sawSyncEvent = false;
 };
 
 this.onsync = function(event) {
-    code = 200;
+    sawSyncEvent = true;
 };