It's currently an ArrayBuffer. Spec change: https://github.com/WICG/digital-identities/pull/97/
<rdar://problem/126244545>
Pull request: https://github.com/WebKit/WebKit/pull/27125
Committed 277379@main (24aaf367721d): <https://commits.webkit.org/277379@main> Reviewed commits have been landed. Closing PR #27125 and removing active labels.