Add a virtual beamforming audio device on ChromeOS.

media/audio/cras/audio_manager_cras.h

Index: media/audio/cras/audio_manager_cras.h
diff --git a/media/audio/cras/audio_manager_cras.h b/media/audio/cras/audio_manager_cras.h
index 4c8f992ee05a61dc041a49f9a37a6df846986e6d..0a9135c522bb7f158b0c69398fd1e3a76182c096 100644
--- a/media/audio/cras/audio_manager_cras.h
+++ b/media/audio/cras/audio_manager_cras.h
@@ -61,6 +61,12 @@ class MEDIA_EXPORT AudioManagerCras : public AudioManagerBase {
 
   bool has_keyboard_mic_;
 
+  // Holds the name and ID of a virtual beamforming device if the machine
+  // indicates it has a mic array by providing a mic positions field.
+  const AudioDeviceName beamforming_device_name_;

[Henrik Grunell, 2015/08/27 08:38:18]

Why is it restricted to only the default device?

Does it make sense to abstract a device, instead of hard coding the virtual one
here?

[ajm, 2015/08/28 07:36:13]

AudioManagerCras only exposes a single device called "Default" today. Not sure
exactly what you mean by "abstract a device".

[aluebs-chromium, 2015/08/28 19:14:30]

Do these really need to be part of the state of this class? Or can't you just
query or concatenate them when needed?

[ajm, 2015/08/28 23:38:31]

They're immutable, so we're not expanding the "state-space" if you will. I don't
mind computing beamforming_device_name_ on demand, but I'd prefer to leave
mic_positions_ as a member to avoid the unknown complexity of querying CRAS for
the device list.

[aluebs-chromium, 2015/08/29 00:00:26]

Agreed.

+  // Stores the mic positions field from the device.

[Henrik Grunell, 2015/08/27 08:38:18]

Nit: Empty line before comment.

+  const std::string mic_positions_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioManagerCras);
 };