In case a custom property used in an animation's keyframes changes its registration, we should recompute the keyframes.
Pull request: https://github.com/WebKit/WebKit/pull/9447
Committed 259737@main (70fad0325901): <https://commits.webkit.org/259737@main> Reviewed commits have been landed. Closing PR #9447 and removing active labels.
<rdar://problem/104947453>