[ServiceWorker] A header/something to kill SWs (#614)

Spin off from #468.
Alex:
>  I a conversation I had with @metromoxie makes me think we should also add a special none or blank
> value to Service-Worker-Allowed to disable SWs entirely. Many users want a similar kill-switch.

> I'd be happy with a different header to kill things, but something seems necessary.

Anne:
> I had the impression unregister() was the way to remove a single service worker and there would be no protocol equivalent.
>
> If we want a protocol solution to removing a service worker, using HTTP 410 seems much more applicable.
>
> Using none as keyword to forbid service workers of any kind seems fine although it's a bit unclear to me how you disambiguate that from a relative URL. Would we require URLs in that header to start with a slash?

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Reply to this email directly or view it on GitHub:
https://github.com/slightlyoff/ServiceWorker/issues/614