Default camera whose facingMode is unknown should be selected by getUserMedia if there is no facingMode constraint
<rdar://problem/108045715>
Pull request: https://github.com/WebKit/WebKit/pull/12740
Committed 263022@main (302d5fe7dea9): <https://commits.webkit.org/263022@main> Reviewed commits have been landed. Closing PR #12740 and removing active labels.