fast/text/variations/getComputedStyle.html semi-frequently times out: https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=fast%2Ftext%2Fvariations%2FgetComputedStyle.html Looking at the code, this appears to be an actual problem with font.loaded promise not getting resolved - there is nothing timing sensitive in the test itself.
<rdar://problem/31393842>