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

LayoutTests/http/tests/serviceworker/controller-on-reload.html

Index: LayoutTests/http/tests/serviceworker/controller-on-reload.html
diff --git a/LayoutTests/http/tests/serviceworker/controller-on-reload.html b/LayoutTests/http/tests/serviceworker/controller-on-reload.html
index deec0b3ba26cbaec7db68bc072b17c62679fd5c3..549d45869e90ff8dadaef2ee2f3457e638cb85de 100644
--- a/LayoutTests/http/tests/serviceworker/controller-on-reload.html
+++ b/LayoutTests/http/tests/serviceworker/controller-on-reload.html
@@ -27,10 +27,7 @@ t.step(function() {
         w.navigator.serviceWorker.register('empty-worker.js',
                                            {scope: 'blank.html'})
         .then(function(registration) {
-            return wait_for_update(t, registration);
-          })
-        .then(function(worker) {
-            return wait_for_state(t, worker, 'activated');
+            return wait_for_state(t, registration.installing, 'activated');
           })
         .then(function() {
             assert_equals(w.navigator.serviceWorker.controller, null,