It's hard to see anything obvious here. I compared the triggering build and the one before:
https://build.chromium.org/p/chromium.webrtc.fyi/builders/Mac%20Tester/builds/29907
https://build.chromium.org/p/chromium.webrtc.fyi/builders/Mac%20Tester/builds/29908
That gives me the WebRTC revision interval #12698:12700.

The changes in that range are:
https://chromium.googlesource.com/external/webrtc/+/50b5c3be844ef571a28b2681c549443a26735d72  (perkj)
https://chromium.googlesource.com/external/webrtc/+/b1fc54d33e109b9bab10114b3aa0d47eb90b799d (peah)

I think only the first of the two could have any affect on video frames throughput. The metric means the number of frames that gets repeated at least once (like a frozen frame counts as repeated).