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.

Reviews requested,
jennyz@,hychao@ - overall review
zelidrag@ - OWNERS review for chromeos/dbus
asargent@ - OWNERS review for c/b/e/api/audio

R=asargent@chromium.org, hychao@chromium.org, jennyz@chromium.org, zelidrag@chromium.org
BUG=397664

[hychao, 2014-08-12 10:47:40]

https://codereview.chromium.org/460113003/diff/1/chrome/browser/extensions/ap...
File chrome/browser/extensions/api/audio/audio_service_chromeos.cc (right):

https://codereview.chromium.org/460113003/diff/1/chrome/browser/extensions/ap...
chrome/browser/extensions/api/audio/audio_service_chromeos.cc:155:
active_output_node_ids.push_back(device.id);
The push_back calls should be pulled out from if/else clause, or there'll  be at
most one device.id push into active_input/output_node_ids.

https://codereview.chromium.org/460113003/diff/1/chrome/browser/extensions/ap...
chrome/browser/extensions/api/audio/audio_service_chromeos.cc:161: // set
correctly to inactive, go through our active devices again and set
I don't see where we deactivate the old active input/output devs( through
RemoveActiveInputNode). The SwitchToDevice() call above only switches the first
active device, the rest of the previous active devices cause stay active
forever.

[asargent_no_longer_on_chrome, 2014-08-12 18:14:02]

c/b/e/api/audio rubber stamp lgtm

[jennyz, 2014-08-12 18:37:55]

https://codereview.chromium.org/460113003/diff/1/chrome/browser/extensions/ap...
File chrome/browser/extensions/api/audio/audio_service_chromeos.cc (right):

https://codereview.chromium.org/460113003/diff/1/chrome/browser/extensions/ap...
chrome/browser/extensions/api/audio/audio_service_chromeos.cc:151:
active_input_node_ids.push_back(device.id);
Yes, hychao's comment later is right, this line should be out of the
!input_device_set if block, otherwise active_input_node_ids and
active_output_ids will only contain the first input/output node from
|device_list|. Also, for additional active input/output nodes list, it doesn't
need to include the one that is already set active by SetActiveOutput/InputNode,
right? And you also need to remove the previous active input/output nodes,
otherwise, they may stay active.