This is not a feature we should continue to support. As it's been disabled for a long time, let's remove it.
For reference, this was added in https://commits.webkit.org/198565@main.
<rdar://problem/118511541>
Pull request: https://github.com/WebKit/WebKit/pull/20814
Committed 271130@main (bc0bc692bc9e): <https://commits.webkit.org/271130@main> Reviewed commits have been landed. Closing PR #20814 and removing active labels.