Reimplement the AlsaPcmOutputStream and fix the threading issues.

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 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 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);
+};