ServiceWorker: unregister's scope argument should be optional

LayoutTests/http/tests/serviceworker/resources/test-helpers.js

 // Adapter for testharness.js-style tests with Service Workers
 
 function service_worker_test(url, description) {
     var t = async_test(description);
     t.step(function() {
         var scope = 'nonexistent';
         service_worker_unregister_and_register(t, url, scope).then(t.step_func(onRegistered));
 
         function onRegistered(worker) {
             var messageChannel = new MessageChannel();
@@ skipping 46 matching lines @@
             }
             resolve(frame);
         };
         document.body.appendChild(frame);
     });
 }
 
 function normalizeURL(url) {
   return new URL(url, document.location).toString().replace(/#.*$/, '');
 }
+
+function wait_for_state(test, worker, state) {
+    return new Promise(test.step_func(function(resolve, reject) {
+        worker.addEventListener('statechange', test.step_func(function() {
+            if (worker.state === state)
+                resolve(state);
+        }));
+    }));
+}