[ServiceWorker] Install algorithm step 14 should clear waiting worker before updating state to redundant (#851)

The Install algorithm has this currently

```
14) If registration’s waiting worker is not null, then:
  1) Terminate registration’s waiting worker.
  2) Run the Update State algorithm passing registration’s waiting worker and
       redundant as the arguments.
  3) The user agent may abort in-flight requests triggered by registration’s waiting worker. 
15) Set registration’s waiting worker to registration’s installing worker. 
```

It seems the `statechange` event triggered by 14.2 Update State might see the redundant worker still set as `registration.waiting`.  Most other instances of Update State change the registration attribute first.

As a side note, should the `statechange` event see the new service worker in registration.waiting or a null .waiting?

---
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/slightlyoff/ServiceWorker/issues/851