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..c760b5b4bccc8b1ba33f6830b5cc05be0a242b4f 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 the virtual beamforming device.
+  const AudioDeviceName beamforming_device_name_;
+
+  // Stores the mic positions field from the device.
+  std::vector<Point> mic_positions_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioManagerCras);
 };