GBM is a linux technology, for sharing buffers in windows we would need another technology.
Created attachment 459179 [details] Patch
ChangeLog entry in Source/WebCore/ChangeLog contains OOPS!.
Created attachment 459287 [details] Patch for landing
Committed r294155 (250525@main): <https://commits.webkit.org/250525@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 459287 [details].
<rdar://problem/93238378>