Adding microphone volume support to chrome.

media/audio/linux/alsa_input.h

Index: media/audio/linux/alsa_input.h
diff --git a/media/audio/linux/alsa_input.h b/media/audio/linux/alsa_input.h
index c70f0de63cc7892b7212a7080961a451aeedf89a..2c0de4d935bb210801bd230441ef0996305c0f14 100644
--- a/media/audio/linux/alsa_input.h
+++ b/media/audio/linux/alsa_input.h
@@ -36,11 +36,14 @@ class AlsaPcmInputStream : public AudioInputStream {
                      AlsaWrapper* wrapper);
   virtual ~AlsaPcmInputStream();
 
-  // Implementation of AudioOutputStream.
+  // Implementation of AudioInputStream.
   virtual bool Open() OVERRIDE;
   virtual void Start(AudioInputCallback* callback) OVERRIDE;
   virtual void Stop() OVERRIDE;
   virtual void Close() OVERRIDE;
+  virtual void GetMaxMicVolume(double* max_volume) OVERRIDE;
+  virtual void SetMicVolume(double volume) OVERRIDE;
+  virtual void GetMicVolume(double* volume) OVERRIDE;
 
  private:
   // Logs the error and invokes any registered callbacks.
@@ -70,6 +73,8 @@ class AlsaPcmInputStream : public AudioInputStream {
   AudioInputCallback* callback_;  // Valid during a recording session.
   base::Time next_read_time_;  // Scheduled time for the next read callback.
   snd_pcm_t* device_handle_;  // Handle to the ALSA PCM recording device.
+  snd_mixer_t* mixer_handle_; // Handle to the ALSA microphone mixer.
+  snd_mixer_elem_t* mixer_element_handle_; // Handle to the capture element.
   base::WeakPtrFactory<AlsaPcmInputStream> weak_factory_;
   scoped_array<uint8> audio_packet_;  // Buffer used for reading audio data.
   bool read_callback_behind_schedule_;