The following layout tests are flaky on Mojave WK1 fast/repaint/fixed.html fast/repaint/fixed-to-relative-position-with-absolute-child.html fast/repaint/fixed-scale.html fast/repaint/absolute-position-changed.html Probable cause: These four image tests fail in tandem. All three tests seem to be drawing boxes, and incorrectly zooming in on the results. Flakiness Dashboard: https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=fast%2Frepaint%2Ffixed.html%20fast%2Frepaint%2Ffixed-to-relative-position-with-absolute-child.html%20fast%2Frepaint%2Ffixed-scale.html%20fast%2Frepaint%2Fabsolute-position-changed.html Links to image diffs: fast/repaint/absolute-position-changed.html https://build.webkit.org/results/Apple%20Mojave%20Release%20WK1%20(Tests)/r239577%20(1897)/fast/repaint/absolute-position-changed-diffs.html fast/repaint/fixed-scale.html https://build.webkit.org/results/Apple%20Mojave%20Release%20WK1%20(Tests)/r239577%20(1897)/fast/repaint/fixed-scale-diffs.html fast/repaint/fixed-to-relative-position-with-absolute-child.html https://build.webkit.org/results/Apple%20Mojave%20Release%20WK1%20(Tests)/r239577%20(1897)/fast/repaint/fixed-to-relative-position-with-absolute-child-diffs.html fast/repaint/fixed.html https://build.webkit.org/results/Apple%20Mojave%20Release%20WK1%20(Tests)/r239577%20(1897)/fast/repaint/fixed-diffs.html
The symptoms here look very similar to https://bugs.webkit.org/show_bug.cgi?id=192881, where the "actual" image is blank white.
I have been unable to reproduce the failures with either running the four tests continuously, running the whole directory repeatedly on one process, or by running the single test runner they all fail on in one process.