Per comment #6 in bug 100580 (https://bugs.webkit.org/show_bug.cgi?id=100580#c6), the appending of the separator should use appendLiteral(": ").
Created attachment 171286 [details] Patch
Comment on attachment 171286 [details] Patch Clearing flags on attachment: 171286 Committed r132841: <http://trac.webkit.org/changeset/132841>
All reviewed patches have been landed. Closing bug.