Reason for revert:
Re-land the original CL because the reverting it didn't fix the problem.
Original issue's description:
> Revert of Make AudioSinkInterface::Data hold a const pointer to the audio buffer. (patchset #1 id:1 of https://codereview.webrtc.org/2873803002/ )
>
> 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: 38605965bd
>
> TBR=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}
> Committed: c904634823TBR=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/2880663003
Cr-Commit-Position: refs/heads/master@{#18113}
0acebe2238