See bug 33383.
WebCore forwarding headers have a special header guard style.
Thanks for the report!
It looks like the rule here is if dir includes /([^/]*)/ForwardingHeaders/, then the header guard should be
Created attachment 49360 [details]
> Patch v1
This patch just disables header guard checks as I proposed in Comment 3.
Comment on attachment 49360 [details]
Clearing flags on attachment: 49360
Committed r55184: <http://trac.webkit.org/changeset/55184>
All reviewed patches have been landed. Closing bug.