fast/regions/layers/region-removed-during-animation.html is flaky on OS X Yosemite. https://webkit-test-results.appspot.com/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=fast%2Fregions%2Flayers%2Fregion-removed-during-animation.html When it fails, the actual image doesn't have the square drawn at all, it only has explanation text.
Marked as flaky in <http://trac.webkit.org/r177785>.
CSS Regions were removed in Bug 174978.