Issue discovered in #36508 (comment)

The TIMEOUT happens because the document's onload event is never fired due to pending blocking loads for the wav.wav audio loaded by the test. It seems like the code in handle_player_event

expects at least one PlayerEvent::StateChanged event to be delivered by the media player stack after a PlayerEvent::MetadataUpdated event, but for the wav.wav audio used by the test, this never happens and so we never clear the delaying-the-load-event flag for those loads. For the other audio resources in the test, there are StateChanged events delivered both before and after the MetadataUpdated event, so their flag gets cleared eventually.

It is unclear if the issue lies with the media player stack or in the assumptions about the order of events in htmlmediaelement.rs logic or in that particular wav.wav file. Also, at least on my local Ubuntu 24.04 VM, the media player stack never delivers a MetadataUpdated for wav.wav, which is different from the CI's media stack behavior.