The new test added for the fix to bug 217987 fails on WK1. This is likely a testing issue.
<rdar://problem/70505533>
Created attachment 411964 [details] Patch
Test is also a constant failure on Windows-EWS. Seems to be failing from introduction on this tester Windows-EWS: https://ews-build.webkit.org/#/builders/10 example run: https://ews-build.webkit.org/#/builders/10/builds/39527 Diff: https://ews-build.s3-us-west-2.amazonaws.com/Windows-EWS/r411970-39565/webanimations/accelerated-overlapping-transform-animations-diffs.html Test expectation while investigated: https://trac.webkit.org/changeset/268803/webkit
Committed r268807: <https://trac.webkit.org/changeset/268807>