https://html.spec.whatwg.org/multipage/webappapis.html#queue-a-task is meant to be called from 'in parallel', but it modifies a task queue, which is a normal Infra set, and that task queue is then used from the main thread without synchronization. We should do something to avoid normalizing that kind of race.

It might be fine to just say "Atomically append" task to queue, and matching wording when tasks are dequeued.