Implement unittest for proxies of MediaStreamTrackInterface and MediaStreamInterface.
This cl also change MediaStreamProxy to only allow setting the state from the signaling thread.

BUG=
TEST=

Review URL: http://webrtc-codereview.appspot.com/237001

git-svn-id: http://webrtc.googlecode.com/svn/trunk@794 4adac7df-926f-26a2-2b94-8c16560cd09d
6 files changed