Reason for revert:
Speculative revert: want to see if this causes the regression in https://crbug.com/602621
Original issue's description:
> Make QualityScaler more responsive to downgrades.
>
> Permits going from HD to QVGA in 6 seconds instead of 10. Also adds
> windows for going up quickly in the beginning of a call (before any
> downscaling happens due to bad quality).
>
> BUG=webrtc:5678
> R=glaznev@webrtc.org, stefan@webrtc.org
>
> Committed: https://crrev.com/85829fd90cc4e7a91c9857921b19e8fc126aeb60
> Cr-Commit-Position: refs/heads/master@{#12219}
TBR=glaznev@webrtc.org,stefan@webrtc.org,pbos@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:5678
NOTRY=true
Review URL: https://codereview.webrtc.org/1880103002
Cr-Commit-Position: refs/heads/master@{#12331}
19b4fecf08