[WebAPI] Expose ServiceWorker in Workers

[Rumyra]

Acceptance criteria

• [ ] The listed features are documented sufficiently on MDN
• [x] BCD is updated
• [x] Interactive example and data repos are updated if appropriate
• [ ] The content has been reviewed as needed

For folks helping with Firefox related documentation

• [ ] Set bugs to dev-doc-complete
• [x] Add entry to Firefox release notes for enabled/preview features
• [x] Add/remove entry to Firefox experimental features page for preference/released features

Related Gecko bugs

https://bugzilla.mozilla.org/show_bug.cgi?id=1113522 https://bugzilla.mozilla.org/show_bug.cgi?id=1131324

Other

• [x] Check content open issues to see if any pertain to the subject matter. If there are any that can be closed because of the work, do so. If there are any that can be fixed relatively quickly because of the knowledge from completing this issue and you have time, feel free to go ahead and fix them.

[hamishwillee]

My understanding is that this allows a service worker to get a handle to the service worker of the window that it is loaded into. With this it can get the registrations (the workers associated with the document in different tabs) and send each active registration a message to update itself.

Essentially this provides a mechanism that allows an updated service worker to send a message to all other tabs running the old version of itself, telling them to update to the latest version. This is cool because otherwise you have to wait for every tab to be shut down running the old version.

I still don't fully grok this, but there are some excellent documents on this here:

• https://redfin.engineering/how-to-fix-the-refresh-button-when-using-service-workers-a8e27af6df68
• https://redfin.engineering/service-workers-break-the-browsers-refresh-button-by-default-here-s-why-56f9417694

I'm trying to confirm state of play in https://bugzilla.mozilla.org/show_bug.cgi?id=1113522#c17

Status

• [x] BCD
  • [x] ServiceWorkerContainer - available in workers https://github.com/mdn/browser-compat-data/pull/24993
  • [x] WorkerNavigator.serviceWorker https://github.com/mdn/browser-compat-data/pull/24863
• [ ] Docs
  • [x] #36726
  • [x] Clean ServiceWorkerContainer
  • [ ] - #36726
  • [ ] #36911
  • [ ] Clean ServiceWorkerRegistration - confusing
• [x] Release notes - #36798
• [ ] dev-doc-complete