Reason for revert:
Reverted because it possibly breaks the internal project.
Original issue's description:
> Make AudioSinkInterface::Data hold a const pointer to the audio buffer.
>
> This is in preparation for https://codereview.webrtc.org/2750783004/, where
> requiring a non-const pointer for AudioSinkInterface would force an unmuting
> and zeroing of every frame.
>
> BUG=webrtc:7343
>
> Review-Url: https://codereview.webrtc.org/2873803002
> Cr-Commit-Position: refs/heads/master@{#18107}
> Committed: 38605965bdTBR=solenberg@webrtc.org,henrik.lundin@webrtc.org,yujo@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:7343
Review-Url: https://codereview.webrtc.org/2877013002
Cr-Commit-Position: refs/heads/master@{#18112}
c904634823