The WPT test scroll-animations/scroll-timelines/updating-the-finished-state.html times out. The specific subtest that times out is "Animation finish event is fired again after replaying from start". If run in isolation, it completes fine, but when paired with other tests, it does not. I've noticed in particular that running just the "Updating the finished state when start time is unresolved and did seek = true" subtest in addition reproduces the timeout. That other subtest can really be reduced to just calling `await waitForNextFrame()`. What happens is that wrapping `requestAnimationFrame` in a promise, which is what it does, means that we will schedule a microtask during the next page rendering update to resolve the promise. As it turns out, this is the same page rendering update during which `AnimationTimelinesController::updateAnimationAndSendEvents()` is called and the first `finish` event is enqueued in the subtest that times out. The behavioral difference that I can see is that the event dispatch happens in the microtask mentioned above, whereas in the case where there is no promise involved, the event dispatch happens later, after about 100ms. I'm not sure if that the source of the issue, but just changing from a promise to a simple callback for `requestAnimationFrame` makes the timeout disappear.