Revert H.264 HW encoder setting to CBR mode.

VBR mode does not work well on KK devices - bitrate
deviations from target are too large,

R=wzh@webrtc.org

Review URL: https://codereview.webrtc.org/1270403007 .

Cr-Commit-Position: refs/heads/master@{#9701}
1 file changed