This is the very beginnings of the traversal methods. This implements a lot of the error handling but does not fully implement traversal, only doing basic manual traversals which can be useful for testing.
Pull request: https://github.com/WebKit/WebKit/pull/23586
<rdar://problem/122471643>
Committed 275054@main (a0dd312f71c5): <https://commits.webkit.org/275054@main> Reviewed commits have been landed. Closing PR #23586 and removing active labels.