RTCMediaStreamTrackStats.keyFramesReceived

[henbos]

We have RTCMediaStreamTrackStats.framesReceived which is the count of frames including both key frames and non-key frames.

I propose we add RTCMediaStreamTrackStats.keyFramesReceived which is a counter for only the portion of received frames that are key frames. (Non-key frames = framesReceived - keyFramesReceived.)

[henbos]

The number of key frames can have a large impact on performance, network pacing and other flow mechanism as well as CPU and media quality. It should be useful for diagnosing and be clear how to implement cross browsers.

[vr000m]

keyFramesSent and keyFramesReceived makes sense. what do we do about partial key frames? probably this triggers a FIR (fullIntraFrameRequest)? or what does the receiver do then?