Fix loopback test for case where no constraint is given. R=stefan@webrtc.org TBR=stefan@webrtc.org
Fix loopback test for case where no constraint is given.
R=stefan@webrtc.org
TBR=stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/11619004

Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: e6013bb7be5f9df9673095f5e834f2f9d486d8c9

sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc