Bug 193107

The following layout tests are flaky on Mojave WK1 fast/layers/blank-content-when-child-layer-is-at-negative-big-number.html fast/layers/wrong-clipping-semi-transparent-compositing-layer-on-subpixel-position.html Probable cause: These two tests are failing in tandem. They seem to be drawing something and unexpectedly zooming in on the result. similar to https://bugs.webkit.org/show_bug.cgi?id=192881 and https://bugs.webkit.org/show_bug.cgi?id=193091 Flakiness Dashboard: https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=fast%2Flayers%2Fblank-content-when-child-layer-is-at-negative-big-number.html%20fast%2Flayers%2Fwrong-clipping-semi-transparent-compositing-layer-on-subpixel-position.html Image diffs: fast/layers/blank-content-when-child-layer-is-at-negative-big-number.html https://build.webkit.org/results/Apple%20Mojave%20Release%20WK1%20(Tests)/r239589%20(1907)/fast/layers/blank-content-when-child-layer-is-at-negative-big-number-diffs.html fast/layers/wrong-clipping-semi-transparent-compositing-layer-on-subpixel-position.html https://build.webkit.org/results/Apple%20Mojave%20Release%20WK1%20(Tests)/r239589%20(1907)/fast/layers/wrong-clipping-semi-transparent-compositing-layer-on-subpixel-position-diffs.html