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

media/audio/linux/alsa_wrapper.h

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // AlsaWrapper is a simple stateless class that wraps the alsa library commands
 // we want to use.  It's purpose is to allow injection of a mock so that the
 // higher level code is testable.
 
 #include <alsa/asoundlib.h>
 
 #include "base/basictypes.h"
 
 class AlsaWrapper {
  public:
   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);
   virtual int PcmPrepare(snd_pcm_t* handle);
   virtual int PcmDrop(snd_pcm_t* handle);
   virtual int PcmDelay(snd_pcm_t* handle, snd_pcm_sframes_t* delay);
   virtual snd_pcm_sframes_t PcmWritei(snd_pcm_t* handle,
                                       const void* buffer,
                                       snd_pcm_uframes_t size);
   virtual int PcmRecover(snd_pcm_t* handle, int err, int silent);
   virtual int PcmSetParams(snd_pcm_t* handle, snd_pcm_format_t format,
                            snd_pcm_access_t access, unsigned int channels,
                            unsigned int rate, int soft_resample,
                            unsigned int latency);
   virtual const char* PcmName(snd_pcm_t* handle);
   virtual snd_pcm_sframes_t PcmAvailUpdate(snd_pcm_t* handle);
 
   virtual const char* StrError(int errnum);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AlsaWrapper);
 };