It would appear r289912 caused (differing) build failures for both GTK and WPE when ANGLE WebGL is enabled.
Created attachment 452346 [details] Patch
Committed r290015 (247401@main): <https://commits.webkit.org/247401@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 452346 [details].
<rdar://problem/89084278>