"WebRTC.Call.BitrateReceivedInKbps"
"WebRTC.Call.VideoBitrateReceivedInKbps"
"WebRTC.Call.AudioBitrateReceivedInKbps"
"WebRTC.Call.RtcpBitrateReceivedInBps"
Reports the average of periodically computed bitrates over a call (2 sec interval). Adds possibility to later modify the stats and use/report the periodic bitrates.
BUG=webrtc:5283
Review-Url: https://codereview.webrtc.org/2303763002
Cr-Commit-Position: refs/heads/master@{#14119}