See FIXME in: Document::flushAutofocusCandidates() https://html.spec.whatwg.org/multipage/interaction.html#focusing-steps https://html.spec.whatwg.org/multipage/interaction.html#focusable-area
https://html.spec.whatwg.org/multipage/interaction.html#flush-autofocus-candidates
<rdar://problem/84386002>