[webrtc-stats] How do we handle overflow of metrics (#496)

vr000m has just created a new issue for https://github.com/w3c/webrtc-stats:

== How do we handle overflow of metrics ==
for example packetSent is represented by a 32-bit in RTP/RTCP. If it overflows does the webrtc-stats report:
1. keeps counting up, we are not limited in such cases we use "unsigned long long"
2. become undefined instead of reporting a constant over-range value.


Please view or discuss this issue at https://github.com/w3c/webrtc-stats/issues/496 using your GitHub account