Fix the control flow of update() method

This patch fixes the control flow of registration.update() method such
that the algorithm returns a promise rejected with an exception on error
conditions. Before this patch, the steps rejected a non-returned promise
and aborted the steps right away.

Issue raised through #1152.

docs/index.bs

@@ -475,15 +475,15 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
 
       <dfn method for="ServiceWorkerRegistration"><code>update()</code></dfn> method *must* run these steps:
 
-        1. Let |p| be a <a>promise</a>.
         1. Let |registration| be the [=ServiceWorkerRegistration/service worker registration=].
         1. Let |newestWorker| be the result of running <a>Get Newest Worker</a> algorithm passing |registration| as its argument.
-        1. If |newestWorker| is null, reject |p| with an "{{InvalidStateError}}" exception and abort these steps.
-        1. If the <a>context object</a>'s <a>relevant settings object</a>'s [=environment settings object/global object=] |globalObject| is a {{ServiceWorkerGlobalScope}} object, and |globalObject|'s associated [=ServiceWorkerGlobalScope/service worker=]'s <a>state</a> is *installing*, reject |p| with an "{{InvalidStateError}}" exception and abort these steps.
-        1. Let |job| be the result of running <a>Create Job</a> with *update*, |registration|'s [=service worker registration/scope url=], |newestWorker|'s [=service worker/script url=], |p|, and the <a>context object</a>'s <a>relevant settings object</a>.
+        1. If |newestWorker| is null, return [=a promise rejected with=] an "{{InvalidStateError}}" exception and abort these steps.
+        1. If the <a>context object</a>'s <a>relevant settings object</a>'s [=environment settings object/global object=] |globalObject| is a {{ServiceWorkerGlobalScope}} object, and |globalObject|'s associated [=ServiceWorkerGlobalScope/service worker=]'s <a>state</a> is *installing*, return [=a promise rejected with=] an "{{InvalidStateError}}" exception and abort these steps.
+        1. Let |promise| be a <a>promise</a>.
+        1. Let |job| be the result of running <a>Create Job</a> with *update*, |registration|'s [=service worker registration/scope url=], |newestWorker|'s [=service worker/script url=], |promise|, and the <a>context object</a>'s <a>relevant settings object</a>.
         1. Set |job|'s <a>worker type</a> to |newestWorker|'s [=service worker/type=].
         1. Invoke <a>Schedule Job</a> with |job|.
-        1. Return |p|.
+        1. Return |promise|.
     </section>
 
     <section algorithm="navigator-service-worker-unregister">
@@ -493,10 +493,10 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
 
       <dfn method for="ServiceWorkerRegistration"><code>unregister()</code></dfn> method *must* run these steps:
 
-        1. Let |p| be a <a>promise</a>.
-        1. Let |job| be the result of running <a>Create Job</a> with *unregister*, the [=service worker registration/scope url=] of the [=ServiceWorkerRegistration/service worker registration=], null, |p|, and the <a>context object</a>'s <a>relevant settings object</a>.
+        1. Let |promise| be a <a>promise</a>.
+        1. Let |job| be the result of running <a>Create Job</a> with *unregister*, the [=service worker registration/scope url=] of the [=ServiceWorkerRegistration/service worker registration=], null, |promise|, and the <a>context object</a>'s <a>relevant settings object</a>.
         1. Invoke <a>Schedule Job</a> with |job|.
-        1. Return |p|.
+        1. Return |promise|.
     </section>
 
     <section>