This CL implements the logic behind qualityLimitationReason[1] and qualityLimitationDurations[2] This CL also exposes qualityLimitationReason in the standard getStats() API, but does not expose qualityLimitationDurations because that is blocked on supporting the "record<>" type in RTCStatsMember[3]. [1] https://w3c.github.io/webrtc-stats/#dom-rtcoutboundrtpstreamstats-qualitylimitationreason [2] https://w3c.github.io/webrtc-stats/#dom-rtcoutboundrtpstreamstats-qualitylimitationdurations [3] https://crbug.com/webrtc/10685 TBR=stefan@webrtc.org Bug: webrtc:10451, webrtc:10686 Change-Id: Ifff0be4ddd64eaec23d59c02af99fdbb1feb3841 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/138825 Commit-Queue: Henrik Boström <hbos@webrtc.org> Reviewed-by: Åsa Persson <asapersson@webrtc.org> Reviewed-by: Harald Alvestrand <hta@webrtc.org> Cr-Commit-Position: refs/heads/master@{#28090}