ANGLE could be compiled with "aggressive uninitialised variable" setting Upstream ANGLE is also compiled with it, -Wconditional-uninitialized
Created attachment 429739 [details] Patch
Note that there are important steps to take when updating ANGLE. See https://trac.webkit.org/wiki/UpdatingANGLE
<rdar://78216626>
Committed r278153 (238197@main): <https://commits.webkit.org/238197@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 429739 [details].