PSA: RTCRtpSender/RTCRtpReceiver.getStats() shipping in M67

[hb...@webrtc.org]

The stats selection algorithm is shipping in M67, which exposes three new ways of calling getStats():

• RTCRtpSender.getStats()
• Performs getStats(), filtering using sender as the selector.
• RTCRtpReceiver.getStats()
• Performs getStats(), filtering using receiver as the selector.
• RTCPeerConnection.getStats(optional MediaStreamTrack? selector = null)
• Performs getStats(), optionally filtering using the track's sender or receiver as the selector. The parameterless version of this API which returns the result of a full stats collection is not new, what's new for M67 is being able to specify a MediaStreamTrack selector in the promise-based API.

These APIs return a subset of the result of a full getStats() call, the benefit is convenience and easier being able to find the relevant stats. For example, if you call sender.getStats(), the 'track' stats object contained in the result will be the stats for the sender's track.

In technical jargon, this returns all the stats (spec, list of implemented stats) that are directly or indirectly referenced by any of the selector's outbound-rtp stats objects (if selector is a sender) or inbound-rtp stats objects (if selector is a receiver).