Store audio device's active state in preference

chromeos/audio/audio_devices_pref_handler.h

Index: chromeos/audio/audio_devices_pref_handler.h
diff --git a/chromeos/audio/audio_devices_pref_handler.h b/chromeos/audio/audio_devices_pref_handler.h
index 2347aad6a467c1e7956d7ec9537e8bf186b9d12f..0be562143a2b36b0c6b3da1dafa65e4a1e593cd2 100644
--- a/chromeos/audio/audio_devices_pref_handler.h
+++ b/chromeos/audio/audio_devices_pref_handler.h
@@ -15,6 +15,18 @@ namespace chromeos {
 
 struct AudioDevice;
 
+// Used to represent an audio device's state. This state should be updated
+// to AUDIO_STATE_ACTIVE when it is selected as active or set to
+// AUDIO_STATE_INACTIVE when selected to a different device. When the audio
+// device is unplugged, its last active/inactive state should be stored.
+// The default value of device state will be AUDIO_STATE_NOT_AVAILABLE if
+// the device is not found in the pref settings.
+enum AudioDeviceState {
+  AUDIO_STATE_ACTIVE,

[Daniel Erat, 2016/01/07 17:31:12]

explicitly specify the numbers for these and document that these can't be
renumbered (since that would break existing prefs)

[hychao, 2016/01/11 07:02:32]

Done.

+  AUDIO_STATE_INACTIVE,
+  AUDIO_STATE_NOT_AVAILABLE,
+};
+
 // Interface that handles audio preference related work, reads and writes
 // audio preferences, and notifies AudioPrefObserver for audio preference
 // changes.
@@ -38,6 +50,11 @@ class CHROMEOS_EXPORT AudioDevicesPrefHandler
   // Sets the audio mute value to prefs for a device.
   virtual void SetMuteValue(const AudioDevice& device, bool mute_on) = 0;
 
+  virtual AudioDeviceState GetDeviceState(
+      const AudioDevice &device) = 0;
+  virtual void SetDeviceState(const AudioDevice& device,
+                              AudioDeviceState state) = 0;
+
   // Reads the audio output allowed value from prefs.
   virtual bool GetAudioOutputAllowedValue() = 0;