Move Alsa device opening into the audio thread, and add in support for multi-channel audio.

media/audio/linux/alsa_wrapper.h

Index: media/audio/linux/alsa_wrapper.h
diff --git a/media/audio/linux/alsa_wrapper.h b/media/audio/linux/alsa_wrapper.h
index d7686dd29cfa054d642298bbfe1855d70182e9dd..5ab3c84534b26d093688db907d1d9043c3559b88 100644
--- a/media/audio/linux/alsa_wrapper.h
+++ b/media/audio/linux/alsa_wrapper.h
@@ -15,6 +15,10 @@ class AlsaWrapper {
   AlsaWrapper();
   virtual ~AlsaWrapper();
 
+  virtual int DeviceNameHint(int card, const char* iface, void*** hints);
+  virtual char* DeviceNameGetHint(const void* hint, const char* id);
+  virtual int DeviceNameFreeHint(void** hints);
+
   virtual int PcmOpen(snd_pcm_t** handle, const char* name,
                       snd_pcm_stream_t stream, int mode);
   virtual int PcmClose(snd_pcm_t* handle);