NADA's proposal from Cisco.

The implementation of this proposal is in progress.
More unittest will be added.
Sender side is being implemented.
Some constants need to be tuned.

BUG=4550
R=stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/43299004

Cr-Commit-Position: refs/heads/master@{#9146}
13 files changed