Reason for revert:
Let's revert this while we investigate a problem in H264 bitstream parser.
Original issue's description:
> Add QP for FFmpeg H264 decoder.
>
> BUG=webrtc:6541
>
> Review-Url: https://codereview.webrtc.org/2649133007
> Cr-Commit-Position: refs/heads/master@{#16942}
> Committed: 879f4f6c31
TBR=sprang@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:6541, chromium:697795
Review-Url: https://codereview.webrtc.org/2726973003
Cr-Commit-Position: refs/heads/master@{#16974}