Make WebGL use GPU process on macOS layout tests by default
<rdar://problem/101113326>
Pull request: https://github.com/WebKit/WebKit/pull/5319
Committed 255952@main (0882d1833451): <https://commits.webkit.org/255952@main> Reviewed commits have been landed. Closing PR #5319 and removing active labels.
Re-opened since this is blocked by bug 247077
Pull request: https://github.com/WebKit/WebKit/pull/6924
Committed 257377@main (99c2dd7bfa7e): <https://commits.webkit.org/257377@main> Reviewed commits have been landed. Closing PR #6924 and removing active labels.