Share one thread between all AudioOutputControllers instead of creating one per stream.

media/audio/audio_manager.cc

+// Copyright (c) 2010 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/audio_manager.h"
+
+#include "base/at_exit.h"
+#include "base/logging.h"
+
+namespace {
+
+AudioManager* g_audio_manager = NULL;
+
+// NullAudioManager is the audio manager used on the systems that have no
+// audio support.
+class NullAudioManager : public AudioManager {
+ public:
+  NullAudioManager() { }
+
+  // Implementation of AudioManager.
+  virtual bool HasAudioOutputDevices() { return false; }
+  virtual bool HasAudioInputDevices() { return false; }
+  virtual AudioOutputStream* MakeAudioOutputStream(Format format, int channels,
+                                                   int sample_rate,
+                                                   char bits_per_sample) {
+    NOTIMPLEMENTED();
+    return NULL;
+  }
+  virtual AudioInputStream* MakeAudioInputStream(Format format, int channels,
+                                                 int sample_rate,
+                                                 char bits_per_sample,
+                                                 uint32 samples_per_packet) {
+    NOTIMPLEMENTED();
+    return NULL;
+  }
+  virtual void MuteAll() { NOTIMPLEMENTED(); }
+  virtual void UnMuteAll() { NOTIMPLEMENTED(); }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(NullAudioManager);
+};
+
+}  // namespace
+
+// static
+void AudioManager::Destroy(void* not_used) {
+  delete g_audio_manager;
+  g_audio_manager = NULL;
+}
+
+// static
+AudioManager* AudioManager::GetAudioManager() {
+  if (!g_audio_manager) {
+    g_audio_manager = CreateAudioManager();
+    g_audio_manager->Init();
+    base::AtExitManager::RegisterCallback(&AudioManager::Destroy, NULL);
+  }
+  return g_audio_manager;
+}