The following layout test is flaky on Mojave WK1 Release and Debug media/track/track-css-visible-stroke.html media/track/track-cue-left-align.html media/track/track-cue-line-position.html Probable cause: Unsure of point of regression. The 3 tests above fail in tandem on both queues. I have tried reproducing it by testing each test locally, and using the test runners from those runs and I cannot get them to fail. Looking at the stdio log, media/track/track-css-visible-stroke.html fails first with a reference mismatch, then the other two fail with failed unexpectedly (reference mismatch didn't happen) Flakiness Dashboard: https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=media%2Ftrack%2Ftrack-css-visible-stroke.html%20media%2Ftrack%2Ftrack-cue-left-align.html%20media%2Ftrack%2Ftrack-cue-line-position.html Diff for media/track/track-css-visible-stroke.html: https://build.webkit.org/results/Apple%20Mojave%20Release%20WK1%20(Tests)/r243707%20(4088)/media/track/track-css-visible-stroke-diff.png
<rdar://problem/49501367>
These tests do not appear to be flaky on Mac anymore.