Verifies that the VideoSendStream starts sending the set SSRC over RTP. BUG=2227 R=stefan@webrtc.org Review URL: https://webrtc-codereview.appspot.com/2074004 git-svn-id: http://webrtc.googlecode.com/svn/trunk@4573 4adac7df-926f-26a2-2b94-8c16560cd09d