Reason for revert:
Relanding, now that downstream issues have been fixed.
Original issue's description:
> Revert of Declare VideoCodec.codec_specific_info private (patchset #5 id:80001 of https://codereview.webrtc.org/2452963002/ )
>
> Reason for revert:
> Broke a google3 build
>
> Original issue's description:
> > Declare VideoCodec.codec_specific_info private
> >
> > This completes the privatization of the codec specific
> > information in VideoCodec.
> >
> > BUG=webrtc:6603
> >
> > Committed: https://crrev.com/792738640234d81c916ac4458ac72286cb2548a4
> > Cr-Commit-Position: refs/heads/master@{#15013}
>
> TBR=tommi@chromium.org,magjed@chromium.org,tommi@webrtc.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=webrtc:6603
>
> Committed: https://crrev.com/7fe6db91d99cf6d43874651bcca56092cf869e2f
> Cr-Commit-Position: refs/heads/master@{#15027}
TBR=tommi@chromium.org,magjed@chromium.org,tommi@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:6603
Review-Url: https://codereview.webrtc.org/2494683006
Cr-Commit-Position: refs/heads/master@{#15041}
c63fb3a0d3