captureStreamUntilEnded? (Re: peerIdentity and transparency)

Taking off on a tangent to the discussion:

In a peerIdentity message, Martin referred to captureStreamUntilEnded().

The only spec for this function I can see is in a draft that isn't being
pursued at the moment (as far as I know):

http://www.w3.org/2011/audio/drafts/1WD/MediaStream/

The relevant WebIDL is:

partial interface HTMLMediaElement {
readonly attribute MediaStream stream;

MediaStream captureStream();
MediaStream captureStreamUntilEnded();
attribute boolean captureAudio;

attribute any src;
};

We already took the "src" change from this spec and turned it into
"srcObject", and made it part of our spec. But I haven't seen a proposal
to move captureStream* in the same way.

Is it interesting to think of adopting the captureStream() interface? It
would resolve a long standing issue of "how do I produce a MediaStream
when I don't have a camera", but there might be dragons lying in wait
here that makes this unadvisable at the present time....

               Harald