ServiceWorker cleanup: remove wait_for_update() in favor of r.installing in most tests

LayoutTests/http/tests/serviceworker/resources/fetch-access-control-util.js

 var SCOPE = 'resources/fetch-access-control-iframe.html';
 var BASE_URL = 'http://127.0.0.1:8000/serviceworker/resources/fetch-access-control.php?';
 var OTHER_BASE_URL = 'http://localhost:8000/serviceworker/resources/fetch-access-control.php?';
 var REDIRECT_URL = 'http://127.0.0.1:8000/serviceworker/resources/redirect.php?Redirect=';
 var IFRAME_URL = 'http://127.0.0.1:8000/serviceworker/resources/fetch-access-control-iframe.html';
 var WORKER_URL = 'http://127.0.0.1:8000/serviceworker/resources/fetch-access-control-worker.js';
 var IFRAME_ORIGIN = 'http://127.0.0.1:8000';
 
 // Functions to check the result from the ServiceWorker.
 var checkFetchResult = function(expected, url, data) {
@@ skipping 117 matching lines @@
       var counter = 0;
       window.addEventListener('message', test.step_func(onMessage), false);
 
       Promise.all([login1, login2])
         .then(function() {
             return service_worker_unregister_and_register(test,
                                                           workerScript,
                                                           SCOPE);
           })
         .then(function(registration) {
-            return wait_for_update(test, registration);
-          })
-        .then(function(sw) {
-            worker = sw;
+            worker = registration.installing;
             var messageChannel = new MessageChannel();
             messageChannel.port1.onmessage = test.step_func(onWorkerMessage);
-            sw.postMessage(
+            worker.postMessage(
               {port: messageChannel.port2}, [messageChannel.port2]);
-            return wait_for_state(test, sw, 'activated');
+            return wait_for_state(test, worker, 'activated');
           })
         .then(function() {
             return with_iframe(SCOPE);
           })
         .then(function(frame) {
             frameWindow = frame.contentWindow;
             // Start tests.
             loadNext();
           })
         .catch(unreached_rejection(test));
@@ skipping 52 matching lines @@
             worker.postMessage({msg: 'START TEST CASE'});
           }))
           .then(test.step_func(function() {
               frameWindow.postMessage(
                 {url: TEST_TARGETS[counter][0]},
                 IFRAME_ORIGIN);
             }));
       }
     });
 }