All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=845870

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=e5a8f9d075c26845b3c85f594212945259bffcf5da39b406d3df6433d7090b09


Bot(s) for this bug's original alert(s):

webrtc-mac-large-tests
webrtc-win-large-tests

Of these alerts, some seem related to cl https://webrtc-review.googlesource.com/76921 (framerate controller, #23316). 

Some of the bots have a very large commit range, though, and could also be from the earlier vp9 screensharing case. https://webrtc-review.googlesource.com/76801, #23311.

Please have a look to see of changes are ok, and explained by your vp9 improvements.

screenshare_slides_vp9_2sl - all changes are positive except of dropped_frames which increased from 3 to 40. I'm investigating this.

vp9svc_3sl_medium, vp9svc_3sl_low - PSNR dropped on 5dB. There was issue in libvpx. The issue is fixed in the latest libvpx which was rolled to chromium today.

TOffsetSimulcastRedRtx - negative changes ramp-up-rtx-media-sent.

screenshare_slides_simulcast, screenshare_slides_simulcast_alr - network_time increased. Addressed here - https://bugs.chromium.org/p/chromium/issues/detail?id=845132

Added alerts that occured at the same time and at recovery.