Just waiting for CA to "commit" in the UI process isn't enough, because we still aren't throttled to 60fps, because the UI process runloop is just happily looping away.
Let's use a CADisplayLink and actually throttle the didUpdate reply to 60fps, thus throttling painting (often only barely makes 60fps anyway) and requestAnimationFrame (much more problematic).
Created attachment 234840 [details]
Comment on attachment 234840 [details]
View in context: https://bugs.webkit.org/attachment.cgi?id=234840&action=review
> + _displayLink.paused = true;