It is only referenced in the AppleWin port but the implementation is dependent on WebGL being enabled which is never the case for AppleWin.
Created attachment 425807 [details] Patch
r=mews
Committed r275858 (236423@main): <https://commits.webkit.org/236423@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 425807 [details].
<rdar://problem/76570448>