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_;
+  // Stores the mic positions field from the device.
+  const std::string mic_positions_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioManagerCras);
 };