Just noting that we will be keeping the previous behavior in Firefox. I don’t imagine it will cause any interop issues (hopefully!).

How does that work? Does Firefox violate the HTML spec and run the event loop even in non-active documents?

How does that work?

We monitor if the document becomes non-active and reject the relevant promises.

Does Firefox violate the HTML spec and run the event loop even in non-active documents?

No (maybe). We just don’t leave the promises unsettled.

Well, unless you run the event loop in non-active documents, you can never observe the promise becoming settled, because you have to run the event loop to call any fulfillment/rejection handlers... That's why I was mentioning in #872 (comment) that introducing this requirement was a mess-up.

Ok, I’ll have another read of the architecture discussion. I didn’t read it very closely as I thought it was a limitation in Blink. If it applies to Gecko too, I can remove the code.

Pro-tip: just read my posts in that thread, since they come from someone not as familiar with the Blink architecture, but instead with the spec ^_^.

Ok, I see. I think it should be fine to change Gecko too. I’ll file a bug and do some investigation next week.

https://bugzilla.mozilla.org/show_bug.cgi?id=1567641