Spec: https://www.w3.org/TR/webrtc-stats/#dom-rtcvideosourcestats-frames Wiring up the "frames" stats with the cumulative fps counter on the video source. Tests: ./out/Default/peerconnection_unittests ./out/Default/video_engine_tests Bug: webrtc:12499 Change-Id: I4103f56ed04cb464f5f7e70fbf2d77c25a867a68 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/208782 Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org> Reviewed-by: Henrik Boström <hbos@webrtc.org> Reviewed-by: Erik Språng <sprang@webrtc.org> Commit-Queue: Henrik Boström <hbos@webrtc.org> Cr-Commit-Position: refs/heads/master@{#33404}