ready promise doesn't work right when controlling registration is resurrected

[wanderview]

I was debugging some intermittent failures in our tests when I noticed some strange behavior. Consider:

  // start with a service worker
  let reg = await navigator.serviceWorker.register(script);
  await waitForState(reg.installing, "activated");

  // get a controlled document to hold the worker alive
  let frame = await withIframe(controlledURL);

  // mark the registration as uninstalling, but it won't
  // fully uninstall because of the frame
  await reg.unregister();
  
  // get the ready promise while in the uninstalling state
  let readyPromise = navigator.serviceWorker.ready;

  // register the service worker again, resurrecting the currently
  // active worker
  await navigator.serviceWorker.register(script);

  // this will never resolve
  await readyPromise;

I also wrote up a glitch to test this:

https://sw-ready-resurrection.glitch.me/

It seems both firefox and chrome have this problem. I think we should resolve the ready promise if we resurrect an uninstalling registration with an active worker and matching scope.

[jakearchibald]

Agreed. Good catch!

[jakearchibald]

I love a good reduced test.

[wanderview]

Ok, I'll fix in firefox here:

https://bugzilla.mozilla.org/show_bug.cgi?id=1402085

I have a WPT test there we'll upstream.

[wanderview]

Ok, fix should be in FF58. The WPT test will upstream when we next sync with upstream web-platform-tests.