Add ability to active multiple devices via the audio API.

Add ability to active multiple devices via the audio API.

Add the ability to the audio API to activate more than one audio device at a
time. This is currently accomplished via a hack and when getting device info
via audio.getInfo, only one device will show up as active.

This will allow us to active multiple microphones and multiple speakers though.

I've also made couple of changes to OWNERS files so we don't need to keep
chasing rubberstamps for audio changes.

This is patched from rkc@'s original cl:
https://codereview.chromium.org/460113003/

BUG=397664
TBR=asargent

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=289951

[jennyz, 2014-08-14 21:55:19]

Since rkc@ is not available due to his transferring to NYC, I 've taken his cl
over. Please review the cl, I made some changes based on the comments from the
original cl. 

hychao@, please take a careful look. As we short circuit the CrasAudioHandler
for adding additional active audio nodes, I am still kind of concerned if all
things will work as expected. I thought rkc@ is going to completely cut off
CrasAudioHandler from extension api as a workaround, but it seems he is only
short circuited it for SetActiveDevices API only. I wonder if all the additional
active nodes will have be active when CrasAudioHandler queries audio with
GetNodes.
This may cause problems because it assume there is only one active device.

In the SetActiveDevices API, it only picked first one in the device_list to
SetActiveOutput/InputNode, and CrasAudioHandler only SetOutputNodeVolume and
SetInputNodeGain on the active node set by SetActiveOutput/InputNode, not for
the additonal active nodes, will this become a problem?

I know this is a short term work around, just would like to point out the
potential issues I can think about. Hope this will not be an immediate issue for
hotrod.

[zel, 2014-08-14 21:57:55]

lgtm

[hychao, 2014-08-15 07:19:37]

lgtm

[jennyz, 2014-08-15 16:15:55]

The CQ bit was checked by jennyz@chromium.org

[jennyz, 2014-08-15 16:16:37]

The CQ bit was unchecked by jennyz@chromium.org

[jennyz, 2014-08-15 16:44:54]

The CQ bit was checked by jennyz@chromium.org

[commit-bot: I haz the power, 2014-08-15 16:47:52]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jennyz@chromium.org/478493002/1

[rkc, 2014-08-15 16:56:32]

lgtm
Thanks for taking this over Jenny!

[commit-bot: I haz the power, 2014-08-15 18:22:17]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_chromium_rel_swarming on tryserver.chromium.win
(http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[commit-bot: I haz the power, 2014-08-15 18:41:15]

Committed patchset #1 (1) as 289951