Output device enumeration for Alsa, plus unit test.

media/audio/linux/audio_manager_linux.h

Index: media/audio/linux/audio_manager_linux.h
diff --git a/media/audio/linux/audio_manager_linux.h b/media/audio/linux/audio_manager_linux.h
index d82cbbd4a5172b8ebf59007e61dc8e00595d9b95..2258e81eb92735ae00bf9455e2ab35e459b6e5cd 100644
--- a/media/audio/linux/audio_manager_linux.h
+++ b/media/audio/linux/audio_manager_linux.h
@@ -27,6 +27,8 @@ class MEDIA_EXPORT AudioManagerLinux : public AudioManagerBase {
   virtual void ShowAudioInputSettings() OVERRIDE;
   virtual void GetAudioInputDeviceNames(media::AudioDeviceNames* device_names)
       OVERRIDE;
+  virtual void GetAudioOutputDeviceNames(media::AudioDeviceNames* device_names)
+      OVERRIDE;
   virtual AudioParameters GetInputStreamParameters(
       const std::string& device_id) OVERRIDE;
 
@@ -55,14 +57,22 @@ class MEDIA_EXPORT AudioManagerLinux : public AudioManagerBase {
     kStreamCapture,
   };
 
-  // Gets a list of available ALSA input devices.
-  void GetAlsaAudioInputDevices(media::AudioDeviceNames* device_names);
+  // Gets a list of available ALSA devices.
+  void GetAlsaAudioDevices(StreamType type,
+                           media::AudioDeviceNames* device_names);
 
-  // Gets the ALSA devices' names and ids.
-  void GetAlsaDevicesInfo(void** hint, media::AudioDeviceNames* device_names);
+  // Gets the ALSA devices' names and ids that support streams of the
+  // given type.
+  void GetAlsaDevicesInfo(StreamType type,
+                          void** hint,
+                          media::AudioDeviceNames* device_names);
 
   // Checks if the specific ALSA device is available.
-  bool IsAlsaDeviceAvailable(const char* device_name);
+  static bool IsAlsaDeviceAvailable(StreamType type,
+                                    const char* device_name);
+
+  static const char* UnwantedDeviceTypeWhenEnumerating(
+      StreamType wanted_type);
 
   // Returns true if a device is present for the given stream type.
   bool HasAnyAlsaAudioDevice(StreamType stream);