LayoutTest media/modern-media-controls/slider/slider-styles.html is a flaky timeout https://build.webkit.org/builders/Apple%20Sierra%20Release%20WK1%20(Tests)/builds/1243 https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=media%2Fmodern-media-controls%2Fslider%2Fslider-styles.html
Marked test as flaky in http://trac.webkit.org/projects/webkit/changeset/216153
<rdar://problem/32008918>