RTCStatsCallback[1] should really be a callback function and not a callback interface.

The current implementation of callback interface only supports the callback function case so in practice it works as intended, but when callback function is supported ( issue 569301 ) it should be used instead. Especially if  issue 630986  is resolved and callback interface starts working as intended.

Very low priority. The callback interface (if implemented correctly) adds one more means of calling the the function, and this is for a non-standardized callback function that is meant to go away soon.

[1] https://cs.chromium.org/chromium/src/third_party/WebKit/Source/modules/peerconnection/RTCStatsCallback.idl?q=RTCStatsCallback.idl&sq=package:chromium&dr