The following layout test is flaky on macOS Debug inspector/debugger/tail-deleted-frames-from-vm-entry.html Probable cause: This test has been flaky for a while. It was previously marked as a flaky failure. Flakiness Dashboard: https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=inspector%2Fdebugger%2Ftail-deleted-frames-from-vm-entry.html
Marked test as slow in https://trac.webkit.org/changeset/227365/webkit to see if that takes care of it.