Revert of Made MixerAudioSource a pure interface.

Revert of Made MixerAudioSource a pure interface. (patchset #7 id:350001 of https://codereview.webrtc.org/2396483002/ )

Reason for revert:
breaks chromium FYI

Original issue's description:
> Made MixerAudioSource a pure interface.
>
> This required quite a few small changes in the mixing algorithm
> structure, the mixer interface and the mixer unit tests.
>
> BUG=webrtc:6346
>
> Committed: https://crrev.com/2ae5fdff86b784545cbd724de54bb5ffedde1adf
> Cr-Commit-Position: refs/heads/master@{#14567}

TBR=ivoc@webrtc.org,solenberg@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:6346
Committed: https://crrev.com/a485dabc7869c35c7d5a8a377e518603012ffa48
Cr-Commit-Position: refs/heads/master@{#14568}

[aleloi, 2016-10-07 12:04:41]

The CQ bit was checked by aleloi@webrtc.org

[aleloi, 2016-10-07 12:04:42]

Created Revert of Made MixerAudioSource a pure interface.

[commit-bot: I haz the power, 2016-10-07 12:04:46]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[commit-bot: I haz the power, 2016-10-07 12:04:55]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-10-07 12:05:02]

Description was changed from

==========
Revert of Made MixerAudioSource a pure interface. (patchset #7 id:350001 of
https://codereview.webrtc.org/2396483002/ )

Reason for revert:
breaks chromium FYI

Original issue's description:
> Made MixerAudioSource a pure interface.
> 
> This required quite a few small changes in the mixing algorithm
> structure, the mixer interface and the mixer unit tests.
> 
> BUG=webrtc:6346
> 
> Committed: https://crrev.com/2ae5fdff86b784545cbd724de54bb5ffedde1adf
> Cr-Commit-Position: refs/heads/master@{#14567}

TBR=ivoc@webrtc.org,solenberg@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:6346
==========

to

==========
Revert of Made MixerAudioSource a pure interface. (patchset #7 id:350001 of
https://codereview.webrtc.org/2396483002/ )

Reason for revert:
breaks chromium FYI

Original issue's description:
> Made MixerAudioSource a pure interface.
>
> This required quite a few small changes in the mixing algorithm
> structure, the mixer interface and the mixer unit tests.
>
> BUG=webrtc:6346
>
> Committed: https://crrev.com/2ae5fdff86b784545cbd724de54bb5ffedde1adf
> Cr-Commit-Position: refs/heads/master@{#14567}

TBR=ivoc@webrtc.org,solenberg@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:6346

Committed: https://crrev.com/a485dabc7869c35c7d5a8a377e518603012ffa48
Cr-Commit-Position: refs/heads/master@{#14568}
==========

[commit-bot: I haz the power, 2016-10-07 12:05:03]

Patchset 1 (id:??) landed as
https://crrev.com/a485dabc7869c35c7d5a8a377e518603012ffa48
Cr-Commit-Position: refs/heads/master@{#14568}