[ Tracking for http://www.w3.org/mid/1373012764.3351.8.camel@cumulustier ]

The latest media capture and streams editors draft describes the
noaccess and peerIdentity constraints:
http://dev.w3.org/2011/webrtc/editor/getusermedia.html#isolated-media-streams

But the text is ambiguous as to whether these are constraints on the
MediaStream or per MediaStreamTrack.

Based on my understanding, we want them as constraints for the whole
MediaStream. There are at least two reasons for that:
* they don't fit well with the other track-constraints — e.g. they can't
be optional, and presumably they can't be applied later once the stream
has been obtained
* they influence addStream() which is at the stream level, not at the
track level

If so, they should be removed from the list of registered constraints in
13.1, and instead be added as MediaStreamConstraints in 11.2.1; the text
in "Isolated Media Streams" would also need to be clarified in that
regard.