The following layout tests are failing on Mac imported/w3c/web-platform-tests/html/semantics/embedded-content/media-elements/ready-states/autoplay.html imported/w3c/web-platform-tests/html/semantics/embedded-content/media-elements/error-codes/error.html Probable cause: These two tests were added as part of https://trac.webkit.org/changeset/242595/webkit. They are flakey on introduction. Flakiness Dashboard: https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=imported%2Fw3c%2Fweb-platform-tests%2Fhtml%2Fsemantics%2Fembedded-content%2Fmedia-elements%2Fready-states%2Fautoplay.html%20imported%2Fw3c%2Fweb-platform-tests%2Fhtml%2Fsemantics%2Fembedded-content%2Fmedia-elements%2Ferror-codes%2Ferror.html
marked tests as flakey in: https://trac.webkit.org/changeset/242644/webkit
Additional failing test from the above changes: imported/w3c/web-platform-tests/html/semantics/embedded-content/the-img-element/sizes/parse-a-sizes-attribute-width-1000px.html
marked flakey in: https://trac.webkit.org/changeset/242900/webkit
Tests are now showing up as a flaky failure on iOS Simulator Release and Debug as well. Reproduced with: run-webkit-tests imported/w3c/web-platform-tests/html/semantics/embedded-content/the-img-element/sizes/parse-a-sizes-attribute-width-1000px.html --iterations 500 -f --ios-simulator --exit-after-n-failures=5 Fails 5 within 22 iterations. Diff: https://build.webkit.org/results/Apple%20iOS%2012%20Simulator%20Release%20WK2%20(Tests)/r243794%20(3430)/imported/w3c/web-platform-tests/html/semantics/embedded-content/the-img-element/sizes/parse-a-sizes-attribute-width-1000px-diff.txt
Updated test expectations for iOS in https://trac.webkit.org/changeset/243802/webkit