We've agreed on the shape of this API internally, so let's move it out of the SPI headers so that we can encourage adoption in upcoming releases.
<rdar://problem/75494316>
Created attachment 423406 [details] Patch
This code doesn't build on Windows, so cannot effect its behavior.
Committed r274562: <https://commits.webkit.org/r274562> All reviewed patches have been landed. Closing bug and clearing flags on attachment 423406 [details].