Reduce includes for CustomHeaderFields, I guess these were needed at some point but not anymore.
Created attachment 400913 [details] Patch
Created attachment 401191 [details] Patch
Created attachment 401258 [details] Patch
Created attachment 401259 [details] Patch
Committed r262683: <https://trac.webkit.org/changeset/262683> All reviewed patches have been landed. Closing bug and clearing flags on attachment 401259 [details].
<rdar://problem/64069902>
<rdar://problem/64069903>