Found via code review. Whenever the buffered range is modified, the MediaPlayerPrivateWebM fails to notify the MediaPlayerPrivate that the buffered range got updated. As a consequence, the media element's buffered range will always be empty.
<rdar://problem/118550061>
Pull request: https://github.com/WebKit/WebKit/pull/20659
Committed 270931@main (1021b9500acc): <https://commits.webkit.org/270931@main> Reviewed commits have been landed. Closing PR #20659 and removing active labels.