(In reply to Kai Engert (:KaiE:) from comment #5)
Florian, what's your plan for testing that the code works as expected?
It will be visible in
about:processes, and I don't see how this could regress, so I don't think adding automated tests is worth the effort. But thanks for asking!
https://phabricator.services.mozilla.com/D105990 is a similar change made for the threading code of the JS engine, we landed with "testing-exception-other: this difference is visible to users of the profiler, but I don't think it's worth testing.".
https://phabricator.services.mozilla.com/D106417 (adding thread names to specific threads) landed with "testing-exception-other: The code was tested manually, it can't fail or regress in any meaningful way so it does not warrant dedicated tests."
I think it should be fine to copy this for the testing tag of your bug.