http://trac.webkit.org/changeset/126774 landed support for position: sticky. After some further test fixes, the only remaining differences seem to be related to sub-pixel difference (1px redness). See: http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=fast%2Fcss%2Fsticky%2Fsticky-left-percentage.html http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=fast%2Fcss%2Fsticky%2Fsticky-writing-mode-vertical-rl.html http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=fast%2Fcss%2Fsticky%2Fsticky-writing-mode-vertical-lr.html
Updated TestExpectations in http://trac.webkit.org/changeset/126806