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

media/audio/linux/alsa_wrapper.cc

Index: media/audio/linux/alsa_wrapper.cc
diff --git a/media/audio/linux/alsa_wrapper.cc b/media/audio/linux/alsa_wrapper.cc
index 8463686ee638d6a0ada9efb39ee996cfe932f83f..303a1f1c51b1b39e3cea0e68eabb2c477189fea2 100644
--- a/media/audio/linux/alsa_wrapper.cc
+++ b/media/audio/linux/alsa_wrapper.cc
@@ -17,6 +17,18 @@ int AlsaWrapper::PcmOpen(snd_pcm_t** handle, const char* name,
   return snd_pcm_open(handle, name, stream, mode);
 }
 
+int AlsaWrapper::DeviceNameHint(int card, const char* iface, void*** hints) {
+  return snd_device_name_hint(card, iface, hints);
+}
+
+char* AlsaWrapper::DeviceNameGetHint(const void* hint, const char* id) {
+  return snd_device_name_get_hint(hint, id);
+}
+
+int AlsaWrapper::DeviceNameFreeHint(void** hints) {
+  return snd_device_name_free_hint(hints);
+}
+
 int AlsaWrapper::PcmClose(snd_pcm_t* handle) {
   return snd_pcm_close(handle);
 }