Our logic for workers is a bit off from the spec. We should be firing abort events right away when abort is called, not wait for the main thread to send us its related events. We can do this by ignoring all of the main-thread-sent abort events (save for the loadstarts and upload.loadend, so we know whether we have upload listeners).

We also don't quite follow the spec in other subtler terms that are most easily addressed by updating our implementation to just more closely match the spec-text around the related methods, and reduce the complexity of the code around abort events.

This would let us pass the last three WPTs related to this:

• https://wpt.fyi/results/xhr/abort-after-receive.any.worker.html
• https://wpt.fyi/results/xhr/abort-after-send.any.worker.html
• https://wpt.fyi/results/xhr/abort-during-upload.any.worker.html

I have a patch in progress to do this.

https://treeherder.mozilla.org/jobs?repo=try&revision=6d8d5872b29ff8daa588abd1cfcc0fde354e8043