Implement the ServiceWorker "activate" event during activation

content/test/data/service_worker/worker_activate_rejected.js

Index: content/test/data/service_worker/worker_activate_rejected.js
diff --git a/content/test/data/service_worker/worker_install_rejected.js b/content/test/data/service_worker/worker_activate_rejected.js
similarity index 88%
copy from content/test/data/service_worker/worker_install_rejected.js
copy to content/test/data/service_worker/worker_activate_rejected.js
index c57ab6f542fa3e67484d9535f5fffec968d302ff..a5c0f58ea38aaaa9d3f94c46c3a8175bdef8dada 100644
--- a/content/test/data/service_worker/worker_install_rejected.js
+++ b/content/test/data/service_worker/worker_activate_rejected.js
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-this.oninstall = function(event) {
+this.onactivate = function(event) {
     event.waitUntil(new Promise(function(resolve, reject) {
         setTimeout(reject, 5);
     }));