Revert of Add a media constraint to enable beamforming.

Revert of Add a media constraint to enable beamforming. (patchset #4 id:60001 of https://codereview.chromium.org/833643005/)

Reason for revert:
I had to revert the WebRTC roll
https://codereview.chromium.org/839173004/

And so now this doesn't compile so I'm going to revert it also. Sorry for the hassle, hopefully it's an easy reland.

Original issue's description:
> Add a media constraint to enable beamforming.
>
> Check the ChromeOS model to pass down the correct microphone array geometry.
>
> BUG=405270
>
> Committed: https://crrev.com/0201ae167ae81ba069f4f9a5498d5f95694edc8d
> Cr-Commit-Position: refs/heads/master@{#310777}

TBR=ajm@chromium.org,dalecurtis@chromium.org,aluebs@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=405270
Committed: https://crrev.com/8fbf60bdf5315ecf8e780ef41b59422e7a3cd0b1
Cr-Commit-Position: refs/heads/master@{#310804}

[scottmg, 2015-01-09 18:40:17]

Created Revert of Add a media constraint to enable beamforming.

[commit-bot: I haz the power, 2015-01-09 18:41:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/844983002/1

[commit-bot: I haz the power, 2015-01-09 18:43:19]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-09 18:44:59]

Patchset 1 (id:??) landed as
https://crrev.com/8fbf60bdf5315ecf8e780ef41b59422e7a3cd0b1
Cr-Commit-Position: refs/heads/master@{#310804}

[ajm, 2015-01-09 18:50:40]

lgtm

Arg! Thanks for the details Scott.

[aluebs-chromium, 2015-01-09 18:59:43]

lgtm
Too bad the WebRTC roll had to be reverted. We were depending on that.