media/track/track-mode.html usually runs fast, but occasionally times out on bots. I also saw it time out locally. Bad test? http://webkit-test-results.appspot.com/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=media%2Ftrack%2Ftrack-mode.html
Added an expectation in r182003.
<rdar://problem/23336495>