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

LayoutTests/http/tests/serviceworker/unregister-controller.html

Index: LayoutTests/http/tests/serviceworker/unregister-controller.html
diff --git a/LayoutTests/http/tests/serviceworker/unregister-controller.html b/LayoutTests/http/tests/serviceworker/unregister-controller.html
index 0517fdaad292ac141300ec916e9e4f54c07b11c7..fc05f7763f5914fe733b6a04dead432d58a374ff 100644
--- a/LayoutTests/http/tests/serviceworker/unregister-controller.html
+++ b/LayoutTests/http/tests/serviceworker/unregister-controller.html
@@ -15,10 +15,7 @@ async_test(function(t) {
     service_worker_unregister_and_register(t, worker_url, scope)
       .then(function(r) {
           registration = r;
-          return wait_for_update(t, registration);
-        })
-      .then(function(worker) {
-          return wait_for_state(t, worker, 'activated');
+          return wait_for_state(t, r.installing, 'activated');
         })
       .then(function() {
           return with_iframe(scope);
@@ -52,10 +49,7 @@ async_test(function(t) {
     service_worker_unregister_and_register(t, worker_url, scope)
       .then(function(r) {
           registration = r;
-          return wait_for_update(t, registration);
-        })
-      .then(function(worker) {
-          return wait_for_state(t, worker, 'activated');
+          return wait_for_state(t, r.installing, 'activated');
         })
       .then(function() {
           return registration.unregister();
@@ -85,10 +79,7 @@ async_test(function(t) {
     service_worker_unregister_and_register(t, worker_url, scope)
       .then(function(r) {
           registration = r;
-          return wait_for_update(t, registration);
-        })
-      .then(function(worker) {
-          return wait_for_state(t, worker, 'activated');
+          return wait_for_state(t, r.installing, 'activated');
         })
       .then(function() {
           return with_iframe(scope);