test_audio_worklet_emscripten_locks is flaky

[brendandahl]

[unresponsive test: test_browser.browser.test_audio_worklet_emscripten_locks total unresponsive=1]

https://app.circleci.com/pipelines/github/emscripten-core/emscripten/45542/workflows/9a959eea-d8fb-432c-bb3b-30422dbf5f13/jobs/1020092

[sbc100]

@cwoffenden

[cwoffenden]

How often has it failed? I see these HTTP errors for random tests frequently.

I can take a look but it won’t be for a week or so.

[brendandahl]

We just changed browser tests to not automatically retry on failures, so we don't have a great sense of how often the failures are happening yet.

[brendandahl]

FWIW, I see another audio worklet flake too test_audio_worklet_post_function_closure https://app.circleci.com/pipelines/github/emscripten-core/emscripten/45544/workflows/d8913a61-19da-4a00-af07-21b25712c1e7/jobs/1020135

[cwoffenden]

I recall Sam flagging some Chrome oddity with test_audio_worklet_emscripten_locks so that wouldn't surprise me, but test_audio_worklet_post_function is really basic: it's message passing between main and audio thread using postMessage(), if that fails then there's something else at play.

[cwoffenden]

Fix incoming in #25276 (I put it down to a race condition between the audio thread having a lock spin and the main thread unable to run during this time).

[cwoffenden]

Fix in #25904.