The following layout test is failing on all Chromium dbg fast/regions/seamless-iframe-flowed-into-regions.html This test looks having been flaky for a long time. In debug build, major part of documents sometimes disappear. http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=fast%2Fregions%2Fseamless-iframe-flowed-into-regions.html
Still repros on today's nightly (r151543)
There implementation of seamless iframes was removed. Closing as invalid.