After the patch for bug 210988 lands, there will be one remaining failure in css/css-animations/KeyframeEffect-setKeyframes.tentative.html to address. The remaining failure is caused by AnimationTimeline::updateCSSAnimations() not updating the animation when the underlying @keyframes rule changed. This is due to Animation::animationsMatch not checking on the actual keyframes.
<rdar://problem/62340847>
This got fixed by 234895. *** This bug has been marked as a duplicate of bug 234895 ***