The new tests added under imported/mozilla/css-animations and imported/mozilla/css-transitions are mostly failing reliably, flaky or timing out.
This test is very flaky on iOS Simulator bots: https://build.webkit.org/results/Apple%20iOS%2011%20Simulator%20Debug%20WK2%20(Tests)/r231850%20(4339)/results.html https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=imported%2Fmozilla%2Fcss-transitions%2Ftest_event-dispatch.html
Marked test as flaky on iOS in https://trac.webkit.org/r231875
<rdar://problem/40998118>
The test passes in general but has some flakiness issues on iOS in particular that remain to be addressed.
This may have been fixed by https://trac.webkit.org/changeset/233325 which fixed https://bugs.webkit.org/show_bug.cgi?id=183834.
Committed r233393: <https://trac.webkit.org/changeset/233393>