This was previously only collected for local tracks (RTCOutboundRTPStreamStats.qpSum). Spec: https://w3c.github.io/webrtc-stats/#dom-rtcrtpstreamstats-qpsum This CL also improves some testing in rtcstatscollector_unittest.cc. Default and non-default values are tested in the same unittests, removing the test that was specific to default-values, which was otherwise code duplication. This is a re-land of https://codereview.webrtc.org/2675943002 after dependent CL that was re-landed. BUG=webrtc:7065 TBR=hta@webrtc.org, sakal@webrtc.org Review-Url: https://codereview.webrtc.org/2703503003 Cr-Commit-Position: refs/heads/master@{#16642}