mainThreadCreateLoader() isn't used anywhere. Even there is no implementation for it.
Created attachment 240004 [details] Patch
It seems it was removed by https://trac.webkit.org/changeset/174583.
Comment on attachment 240004 [details] Patch It is a cruft, let's remove it.
Comment on attachment 240004 [details] Patch Clearing flags on attachment: 240004 Committed r174816: <http://trac.webkit.org/changeset/174816>
All reviewed patches have been landed. Closing bug.