Right now new-run-webkit-tests defaults to the appropriate Chromium port for the platform you're running on. It should default to the appropriate Mac port for the version of the Mac you're running.
Created attachment 49667 [details] patch
Comment on attachment 49667 [details] patch We really need to unify our port classes.
Comment on attachment 49667 [details] patch Clearing flags on attachment: 49667 Committed r55341: <http://trac.webkit.org/changeset/55341>
All reviewed patches have been landed. Closing bug.