[Web Animations] Optimize animation resolution to not re-compute whether effects only contain accelerated animation properties

[Antoine Quint]

When resolving animations we re-compute whether all animated properties are accelerated to return the `shouldRecompositeLayer` flag in TreeResolver::createAnimatedElementUpdate. We should be able to expose such a property when keyframes on a KeyframeEffect change and then also store it on KeyframeEffectStack and compute that value when the stack is changed.

[Antoine Quint]

Retitling because it will likely be enough to do it on just KeyframeEffect since we have to iterate through all the effects of a stack when resolving anyway.

[Antoine Quint]

As it turns out KeyframeEffect already caches this information, we just need to use it!

[Antoine Quint]

Created attachment 383154 [details]
Patch

[Dean Jackson]

Comment on attachment 383154 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=383154&action=review

> Source/WebCore/ChangeLog:9
> +        of iterating over an effec'ts animated properties during resolution to get at the same information. 

typo

[Antoine Quint]

Committed r252307: <https://trac.webkit.org/changeset/252307>

[Radar WebKit Bug Importer]

<rdar://problem/57099367>