This denominator doesn't make any semantic sense, it's better to use
real thresholds for when things look "good" or "bad" rather than
fractions of a max QP.
BUG=webrtc:5678
R=danilchap@webrtc.org
Review URL: https://codereview.webrtc.org/1855393005 .
Cr-Commit-Position: refs/heads/master@{#12363}