Reason for revert:
Failing WebRtcVideoQualityBrowserTest.MANUAL_TestVideoQualityVp* tests.
Mac #19383-19392
https://build.chromium.org/p/chromium.webrtc.fyi/builders/Mac%20Tester/builds/42197
Win8 #19383-19385
https://build.chromium.org/p/chromium.webrtc.fyi/builders/Win8%20Tester/builds/1496
Win7 #19383-19385
https://build.chromium.org/p/chromium.webrtc.fyi/builders/Win7%20Tester/builds/9807
Win10 #19383-19385
https://build.chromium.org/p/chromium.webrtc.fyi/builders/Win10%20Tester/builds/8452
Original issue's description:
> Turn off error resilience for VP9 if no spatial or temporal layers are configured and NACK is enabled.
>
> Error resilience is currently always enabled for VP9 which reduces quality.
>
> Reland of https://codereview.webrtc.org/2532053002
>
> BUG=webrtc:6783
>
> Review-Url: https://codereview.webrtc.org/2925253002
> Cr-Commit-Position: refs/heads/master@{#19385}
> Committed: 6b463faccb
TBR=brandtr@webrtc.org,asapersson@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:6783
Review-Url: https://codereview.webrtc.org/2995173002
Cr-Commit-Position: refs/heads/master@{#19399}