These parameters were only needed because of an optimization where file inputs were being added to the DOMFormData as string values containing their filenames if the entry list was being constructed to be used in a urlencoded or text/plain form submission. This optimization was removed in r286427 and those parameters can now be dropped.
Created attachment 445746 [details] Patch
Committed r286447 (244789@main): <https://commits.webkit.org/244789@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 445746 [details].
<rdar://problem/85985842>