Add RTCDataChannelStats and all of its members.
https://w3c.github.io/webrtc-stats/#dcstats-dict*
dictionary RTCDataChannelStats : RTCStats {
DOMString label;
DOMString protocol;
long datachannelid;
RTCDataChannelState state;
unsigned long messagesSent;
unsigned long long bytesSent;
unsigned long messagesReceived;
unsigned long long bytesReceived;
};
Comment 1 by hbos@chromium.org
, Oct 12 2016