Reason for revert:
Investigation complete.
Original issue's description:
> H264BitstreamParser: Log nalu type when parsing slice type fails.
>
> Decreases all parsing failures to a warning because they are not
> critical errors. This is a speculative commit to help diagnose
> why bots are failing.
>
> BUG=chromium:697795
> TBR=stefan@webrtc.org
>
> Review-Url: https://codereview.webrtc.org/2726833005
> Cr-Commit-Position: refs/heads/master@{#16966}
> Committed: 6bce6ad485TBR=stefan@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:697795
Review-Url: https://codereview.webrtc.org/2723883004
Cr-Commit-Position: refs/heads/master@{#16972}