This can happen when switching between multiple streams and a single while getting feedback from the receiver. BUG=2881 TEST=trybots R=mflodman@webrtc.org Review URL: https://webrtc-codereview.appspot.com/7899004 git-svn-id: http://webrtc.googlecode.com/svn/trunk@5486 4adac7df-926f-26a2-2b94-8c16560cd09d