Created attachment 343469 [details] Test case When the Web Animations experimental feature is on (which is now the default in Safari Technology Preview), the keyframe animation in the attached HTML doesn’t run.
Disabling either one of “Web Animations” and “Web Animations and CSS Integration”, or both, makes the bug go away.
<rdar://problem/41418697>
Changing the target element from a <span> to a <div> makes the animation work as expected. We exit early in KeyframeEffectReadOnly::applyPendingAcceleratedActions() because we fail to get a renderer.
Created attachment 343496 [details] Patch
Committed r233164: <https://trac.webkit.org/changeset/233164>