The test animations/unprefixed-events-mixed-with-prefixed.html is flaky as the "animationiteration" event sometimes doesn't appear in the test output. https://results.webkit.org/?suite=layout-tests&test=animations%2Funprefixed-events-mixed-with-prefixed.html
<rdar://problem/67034553>
Created attachment 413155 [details] Patch
Committed r269368: <https://trac.webkit.org/changeset/269368>