Reimplement the AlsaPcmOutputStream and fix the threading issues.

media/audio/linux/alsa_wrapper.cc

+// 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.
+
+#include "media/audio/linux/alsa_wrapper.h"
+
+#include <alsa/asoundlib.h>
+
+AlsaWrapper::AlsaWrapper() {
+}
+
+AlsaWrapper::~AlsaWrapper() {
+}
+
+int AlsaWrapper::PcmOpen(snd_pcm_t** handle, const char* name,
+                         snd_pcm_stream_t stream, int mode) {
+  return snd_pcm_open(handle, name, stream, mode);
+}
+
+int AlsaWrapper::PcmClose(snd_pcm_t* handle) {
+  return snd_pcm_close(handle);
+}
+
+int AlsaWrapper::PcmPrepare(snd_pcm_t* handle) {
+  return snd_pcm_prepare(handle);
+}
+
+int AlsaWrapper::PcmDrop(snd_pcm_t* handle) {
+  return snd_pcm_drop(handle);
+}
+
+snd_pcm_sframes_t AlsaWrapper::PcmWritei(snd_pcm_t* handle,
+                                         const void* buffer,
+                                         snd_pcm_uframes_t size) {
+  return snd_pcm_writei(handle, buffer, size);
+}
+
+int AlsaWrapper::PcmRecover(snd_pcm_t* handle, int err, int silent) {
+  return snd_pcm_recover(handle, err, silent);
+}
+
+const char* AlsaWrapper::PcmName(snd_pcm_t* handle) {
+  return snd_pcm_name(handle);
+}
+
+int AlsaWrapper::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) {
+  return snd_pcm_set_params(handle, format, access, channels, rate,
+                            soft_resample, latency);
+}
+
+snd_pcm_sframes_t AlsaWrapper::PcmAvailUpdate(snd_pcm_t* handle) {
+  return snd_pcm_avail_update(handle);
+}
+
+const char* AlsaWrapper::StrError(int errnum) {
+  return snd_strerror(errnum);
+}