test: another attempt to fix sw test #2201

test/assets/serviceworkers/fetch/sw.html

@@ -1,4 +1,5 @@
 <link rel="stylesheet" href="./style.css">
 <script>
   window.registrationPromise = navigator.serviceWorker.register('sw.js');
+  window.activationPromise = new Promise(resolve => navigator.serviceWorker.oncontrollerchange = resolve);
 </script>

test/assets/serviceworkers/fetch/sw.js

@@ -1,3 +1,7 @@
 self.addEventListener('fetch', event => {
   event.respondWith(fetch(event.request));
 });
+
+self.addEventListener('activate', event => {
+  event.waitUntil(clients.claim());
+});