On http://bugs.webkit.org/, the URL field is not linkified if a data: URL is present.
I guess this is fixed in later versions of Bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=276907
Going to mark this as a duplicate of Bug 17457 since it will be fixed in the upgrade. *** This bug has been marked as a duplicate of 17457 ***