Spotted by @yutakahirano in w3c/webtransport#127 (comment)

Documents clean up their WebSockets, EventSource, and timers as part of the "unloading document cleanup steps".

Workers only clean up their timers, at the end of run a worker after their event loop has shut down.

So per spec I believe the server is never told about a WebSocket connection disappearing if that connection is initiated by a worker. Is that what people implement?

What about EventSource? That seems like less of an issue since it just relies on termininating a fetch algorithm, and in general we probably want to terminate a lot of fetch algorithms (which is not well-specified now).

I think it would be nice to introduce "global object cleanup steps" which specs like WebTransport could use for the purposes discussed there, and maybe we could move WebSocket/EventSource/timer cleanup there. That way they don't need to separately hook into window/shared worker/service worker/dedicated worker cleanup locations.

But the details might be tricky, e.g. documents deal with bfcache and the salveagable state in a special way (/cc @rakina @fergal), and we probably want spec authors to think through that interaction in some detail. Similarly shared/service workers might have different considerations than dedicated workers. So I'm not sure.