GraphicsContextGLCocoa does not signal context loss immediately on failed prepare
<rdar://problem/107553596>
Pull request: https://github.com/WebKit/WebKit/pull/12313
Committed 263297@main (a2684c1fef12): <https://commits.webkit.org/263297@main> Reviewed commits have been landed. Closing PR #12313 and removing active labels.