The client previously desired to add SPI to WKPageRef for this, but WKBrowsingContextHandle turns out to work out better.
<rdar://problem/95814743>
Pull request: https://github.com/WebKit/WebKit/pull/1752
Committed 251840@main (b791516ec899): <https://commits.webkit.org/251840@main> Reviewed commits have been landed. Closing PR #1752 and removing active labels.