[Web Animations] Accelerated animations don't run until their natural completion
Created attachment 389535 [details]
So webanimations/opacity-accelerated-animation-finishes-before-removal.html is failing on WK1, which is expected since it doesn't composite opacity animations alone. Will use "transform" instead when landing so that it works across both WK1 and WK2.
Committed r255593: <https://trac.webkit.org/changeset/255593>