Once bug #97037 lands, the Mac port will need to add support (by defining a new CDMPrivate).
The comment says this is a Mac port issue, but the title sys Chromium. Which is right?
I think the comment was just copied from issue 109318. I assume this was in fact for Chromium, so I've closed it.
The Chromium work is tracked in http://crbug.com/224791.