Update bundle behavior to match BundlePolicy spec in http://rtcweb-wg.github.io/jsep/.

BUG=1574
R=juberti@webrtc.org, pthatcher@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/36659004

Cr-Commit-Position: refs/heads/master@{#8851}
5 files changed