Default width of 100% has been removed in changeset 114640 (http://trac.webkit.org/changeset/114640), which affects default caption position (they are no longer centered).
Created attachment 138092 [details]
Comment on attachment 138092 [details]
Clearing flags on attachment: 138092
Committed r114760: <http://trac.webkit.org/changeset/114760>
All reviewed patches have been landed. Closing bug.