The following layout test is flaky on macOS http/tests/websocket/tests/hybi/inspector/before-load.html Probable cause: Unknown, this test only times out a few times every week or two. Flakiness Dashboard: https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=http%2Ftests%2Fwebsocket%2Ftests%2Fhybi%2Finspector%2Fbefore-load.html