Document.baseURI is inaccurate for iframe srcdoc documents: - https://html.spec.whatwg.org/#fallback-base-url
Created attachment 435226 [details] Patch
Created attachment 435264 [details] Patch
Committed r280855 (240398@main): <https://commits.webkit.org/240398@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 435264 [details].
<rdar://problem/81752669>