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

LayoutTests/http/tests/serviceworker/unregister-then-register.html

Index: LayoutTests/http/tests/serviceworker/unregister-then-register.html
diff --git a/LayoutTests/http/tests/serviceworker/unregister-then-register.html b/LayoutTests/http/tests/serviceworker/unregister-then-register.html
index 3b894ae9411fed25c839cfc3755a0ac7fc48c81a..08dd8c3a7eb3efa4de44667df309ed729f0aeeca 100644
--- a/LayoutTests/http/tests/serviceworker/unregister-then-register.html
+++ b/LayoutTests/http/tests/serviceworker/unregister-then-register.html
@@ -13,10 +13,7 @@ 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();
@@ -39,10 +36,7 @@ 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);
@@ -71,10 +65,7 @@ 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);
@@ -108,10 +99,7 @@ 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);