Seems to be somehow caused by http://trac.webkit.org/changeset/164830. The test passes locally in debug builds of DRT and WKTR, and fails in release builds of both.
Committed r164843: <http://trac.webkit.org/changeset/164843>
webkit-patch got a little confused.
Created attachment 225675 [details]
Waiting for this to go through EWS to make sure it's not obviously flaky.
Comment on attachment 225675 [details]
Clearing flags on attachment: 225675
Committed r165004: <http://trac.webkit.org/changeset/165004>
All reviewed patches have been landed. Closing bug.
This test is still failing most of the time, filed bug 129639.