Revert 57254 - Share one thread between all AudioOutputControllers instead of creating one per stream.

TEST=unittests
BUG=39825

Review URL: http://codereview.chromium.org/3185022

TBR=sergeyu@chromium.org
Review URL: http://codereview.chromium.org/3192017

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@57256 0039d316-1c4b-4281-b951-d872f2087c98

23 files changed, 228 insertions, 352 deletions

diff --git a/media/audio/audio_input_controller.h b/media/audio/audio_input_controller.h
index deded58..a00e2bc 100644
--- a/media/audio/audio_input_controller.h
+++ b/media/audio/audio_input_controller.h
@@ -10,7 +10,6 @@
 #include "base/scoped_ptr.h"
 #include "base/thread.h"
 #include "media/audio/audio_io.h"
-#include "media/audio/audio_manager.h"
 
 // An AudioInputController controls an AudioInputStream and records data
 // from this input stream. It has an important function that it executes
diff --git a/media/audio/audio_io.h b/media/audio/audio_io.h
index 4f23686..6e1e289 100644
--- a/media/audio/audio_io.h
+++ b/media/audio/audio_io.h
@@ -153,4 +153,80 @@ class AudioInputStream {
   virtual ~AudioInputStream() {}
 };
 
+// Manages all audio resources. In particular it owns the AudioOutputStream
+// objects. Provides some convenience functions that avoid the need to provide
+// iterators over the existing streams.
+class AudioManager {
+ public:
+  enum Format {
+    AUDIO_PCM_LINEAR = 0,     // PCM is 'raw' amplitude samples.
+    AUDIO_PCM_LOW_LATENCY,    // Linear PCM, low latency requested.
+    AUDIO_MOCK,               // Creates a dummy AudioOutputStream object.
+    AUDIO_LAST_FORMAT         // Only used for validation of format.
+  };
+
+  // Telephone quality sample rate, mostly for speech-only audio.
+  static const uint32 kTelephoneSampleRate = 8000;
+  // CD sampling rate is 44.1 KHz or conveniently 2x2x3x3x5x5x7x7.
+  static const uint32 kAudioCDSampleRate = 44100;
+  // Digital Audio Tape sample rate.
+  static const uint32 kAudioDATSampleRate = 48000;
+
+  // Returns true if the OS reports existence of audio devices. This does not
+  // guarantee that the existing devices support all formats and sample rates.
+  virtual bool HasAudioOutputDevices() = 0;
+
+  // Returns true if the OS reports existence of audio recording devices. This
+  // does not guarantee that the existing devices support all formats and
+  // sample rates.
+  virtual bool HasAudioInputDevices() = 0;
+
+  // Factory for all the supported stream formats. The |channels| can be 1 to 5.
+  // The |sample_rate| is in hertz and can be any value supported by the
+  // platform. For some future formats the |sample_rate| and |bits_per_sample|
+  // can take special values.
+  // Returns NULL if the combination of the parameters is not supported, or if
+  // we have reached some other platform specific limit.
+  //
+  // AUDIO_PCM_LOW_LATENCY can be passed to this method and it has two effects:
+  // 1- Instead of triple buffered the audio will be double buffered.
+  // 2- A low latency driver or alternative audio subsystem will be used when
+  //    available.
+  //
+  // Do not free the returned AudioOutputStream. It is owned by AudioManager.
+  virtual AudioOutputStream* MakeAudioOutputStream(Format format, int channels,
+                                                   int sample_rate,
+                                                   char bits_per_sample) = 0;
+
+  // Factory to create audio recording streams.
+  // |channels| can be 1 or 2.
+  // |sample_rate| is in hertz and can be any value supported by the platform.
+  // |bits_per_sample| can be any value supported by the platform.
+  // |samples_per_packet| is in hertz as well and can be 0 to |sample_rate|,
+  // with 0 suggesting that the implementation use a default value for that
+  // platform.
+  // Returns NULL if the combination of the parameters is not supported, or if
+  // we have reached some other platform specific limit.
+  //
+  // Do not free the returned AudioInputStream. It is owned by AudioManager.
+  // When you are done with it, call |Stop()| and |Close()| to release it.
+  virtual AudioInputStream* MakeAudioInputStream(Format format, int channels,
+                                                 int sample_rate,
+                                                 char bits_per_sample,
+                                                 uint32 samples_per_packet) = 0;
+
+  // Muting continues playback but effectively the volume is set to zero.
+  // Un-muting returns the volume to the previous level.
+  virtual void MuteAll() = 0;
+  virtual void UnMuteAll() = 0;
+
+  // Get AudioManager singleton.
+  // TODO(cpu): Define threading requirements for interacting with AudioManager.
+  static AudioManager* GetAudioManager();
+
+ protected:
+  virtual ~AudioManager() {}
+};
+
+
 #endif  // MEDIA_AUDIO_AUDIO_IO_H_
diff --git a/media/audio/audio_manager.cc b/media/audio/audio_manager.cc
deleted file mode 100644
index 7148d21..0000000
--- a/media/audio/audio_manager.cc
+++ /dev/null
@@ -1,59 +0,0 @@
-// 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;
-}
diff --git a/media/audio/audio_manager.h b/media/audio/audio_manager.h
deleted file mode 100644
index 2185950..0000000
--- a/media/audio/audio_manager.h
+++ /dev/null
@@ -1,101 +0,0 @@
-// 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.
-
-#ifndef MEDIA_AUDIO_AUDIO_MANAGER_H_
-#define MEDIA_AUDIO_AUDIO_MANAGER_H_
-
-#include "base/basictypes.h"
-
-class AudioInputStream;
-class AudioOutputStream;
-class MessageLoop;
-
-// Manages all audio resources. In particular it owns the AudioOutputStream
-// objects. Provides some convenience functions that avoid the need to provide
-// iterators over the existing streams.
-class AudioManager {
- public:
-  enum Format {
-    AUDIO_PCM_LINEAR = 0,     // PCM is 'raw' amplitude samples.
-    AUDIO_PCM_LOW_LATENCY,    // Linear PCM, low latency requested.
-    AUDIO_MOCK,               // Creates a dummy AudioOutputStream object.
-    AUDIO_LAST_FORMAT         // Only used for validation of format.
-  };
-
-  // Telephone quality sample rate, mostly for speech-only audio.
-  static const uint32 kTelephoneSampleRate = 8000;
-  // CD sampling rate is 44.1 KHz or conveniently 2x2x3x3x5x5x7x7.
-  static const uint32 kAudioCDSampleRate = 44100;
-  // Digital Audio Tape sample rate.
-  static const uint32 kAudioDATSampleRate = 48000;
-
-  // Returns true if the OS reports existence of audio devices. This does not
-  // guarantee that the existing devices support all formats and sample rates.
-  virtual bool HasAudioOutputDevices() = 0;
-
-  // Returns true if the OS reports existence of audio recording devices. This
-  // does not guarantee that the existing devices support all formats and
-  // sample rates.
-  virtual bool HasAudioInputDevices() = 0;
-
-  // Factory for all the supported stream formats. The |channels| can be 1 to 5.
-  // The |sample_rate| is in hertz and can be any value supported by the
-  // platform. For some future formats the |sample_rate| and |bits_per_sample|
-  // can take special values.
-  // Returns NULL if the combination of the parameters is not supported, or if
-  // we have reached some other platform specific limit.
-  //
-  // AUDIO_PCM_LOW_LATENCY can be passed to this method and it has two effects:
-  // 1- Instead of triple buffered the audio will be double buffered.
-  // 2- A low latency driver or alternative audio subsystem will be used when
-  //    available.
-  //
-  // Do not free the returned AudioOutputStream. It is owned by AudioManager.
-  virtual AudioOutputStream* MakeAudioOutputStream(Format format, int channels,
-                                                   int sample_rate,
-                                                   char bits_per_sample) = 0;
-
-  // Factory to create audio recording streams.
-  // |channels| can be 1 or 2.
-  // |sample_rate| is in hertz and can be any value supported by the platform.
-  // |bits_per_sample| can be any value supported by the platform.
-  // |samples_per_packet| is in hertz as well and can be 0 to |sample_rate|,
-  // with 0 suggesting that the implementation use a default value for that
-  // platform.
-  // Returns NULL if the combination of the parameters is not supported, or if
-  // we have reached some other platform specific limit.
-  //
-  // Do not free the returned AudioInputStream. It is owned by AudioManager.
-  // When you are done with it, call |Stop()| and |Close()| to release it.
-  virtual AudioInputStream* MakeAudioInputStream(Format format, int channels,
-                                                 int sample_rate,
-                                                 char bits_per_sample,
-                                                 uint32 samples_per_packet) = 0;
-
-  // Muting continues playback but effectively the volume is set to zero.
-  // Un-muting returns the volume to the previous level.
-  virtual void MuteAll() = 0;
-  virtual void UnMuteAll() = 0;
-
-  // Returns message loop used for audio IO.
-  virtual MessageLoop* GetMessageLoop() = 0;
-
-  // Get AudioManager singleton.
-  // TODO(cpu): Define threading requirements for interacting with AudioManager.
-  static AudioManager* GetAudioManager();
-
- protected:
-  virtual ~AudioManager() {}
-
-  // Called from GetAudioManager() to initialiaze the instance.
-  virtual void Init() = 0;
-
- private:
-  static void Destroy(void*);
-
-  // Called by GetAudioManager() to create platform-specific audio manager.
-  static AudioManager* CreateAudioManager();
-};
-
-#endif  // MEDIA_AUDIO_AUDIO_MANAGER_H_
diff --git a/media/audio/audio_manager_base.cc b/media/audio/audio_manager_base.cc
deleted file mode 100644
index 7fa4761..0000000
--- a/media/audio/audio_manager_base.cc
+++ /dev/null
@@ -1,19 +0,0 @@
-// 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_base.h"
-
-AudioManagerBase::AudioManagerBase()
-    : audio_thread_("AudioThread"),
-      initialized_(false) {
-}
-
-void AudioManagerBase::Init() {
-  initialized_ = audio_thread_.Start();
-}
-
-MessageLoop* AudioManagerBase::GetMessageLoop() {
-  DCHECK(initialized_);
-  return audio_thread_.message_loop();
-}
diff --git a/media/audio/audio_manager_base.h b/media/audio/audio_manager_base.h
deleted file mode 100644
index ed8ab0e..0000000
--- a/media/audio/audio_manager_base.h
+++ /dev/null
@@ -1,35 +0,0 @@
-// 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.
-
-#ifndef MEDIA_AUDIO_AUDIO_MANAGER_BASE_H_
-#define MEDIA_AUDIO_AUDIO_MANAGER_BASE_H_
-
-#include "base/thread.h"
-#include "media/audio/audio_manager.h"
-
-// AudioManagerBase provides AudioManager functions common for all platforms.
-class AudioManagerBase : public AudioManager {
- public:
-  AudioManagerBase();
-
-  virtual void Init();
-
-  virtual MessageLoop* GetMessageLoop();
-
- protected:
-  virtual ~AudioManagerBase() {}
-
-  bool initialized() { return initialized_; }
-
- protected:
-  // Thread used to interact with AudioOutputStreams created by this
-  // audio manger.
-  base::Thread audio_thread_;
-
-  bool initialized_;
-
-  DISALLOW_COPY_AND_ASSIGN(AudioManagerBase);
-};
-
-#endif  // MEDIA_AUDIO_AUDIO_MANAGER_BASE_H_
diff --git a/media/audio/audio_output_controller.cc b/media/audio/audio_output_controller.cc
index 27938f9..74e2261 100644
--- a/media/audio/audio_output_controller.cc
+++ b/media/audio/audio_output_controller.cc
@@ -4,8 +4,6 @@
 
 #include "media/audio/audio_output_controller.h"
 
-#include "base/message_loop.h"
-
 // The following parameters limit the request buffer and packet size from the
 // renderer to avoid renderer from requesting too much memory.
 static const uint32 kMegabytes = 1024 * 1024;
@@ -37,12 +35,12 @@ AudioOutputController::AudioOutputController(EventHandler* handler,
                                              uint32 capacity,
                                              SyncReader* sync_reader)
     : handler_(handler),
-      stream_(NULL),
       volume_(1.0),
       state_(kEmpty),
       hardware_pending_bytes_(0),
       buffer_capacity_(capacity),
-      sync_reader_(sync_reader) {
+      sync_reader_(sync_reader),
+      thread_("AudioOutputControllerThread") {
 }
 
 AudioOutputController::~AudioOutputController() {
@@ -67,9 +65,10 @@ scoped_refptr<AudioOutputController> AudioOutputController::Create(
   scoped_refptr<AudioOutputController> controller = new AudioOutputController(
       event_handler, buffer_capacity, NULL);
 
-  controller->message_loop_ =
-      AudioManager::GetAudioManager()->GetMessageLoop();
-  controller->message_loop_->PostTask(
+  // Start the audio controller thread and post a task to create the
+  // audio stream.
+  controller->thread_.Start();
+  controller->thread_.message_loop()->PostTask(
       FROM_HERE,
       NewRunnableMethod(controller.get(), &AudioOutputController::DoCreate,
                         format, channels, sample_rate, bits_per_sample,
@@ -97,9 +96,10 @@ scoped_refptr<AudioOutputController> AudioOutputController::CreateLowLatency(
   scoped_refptr<AudioOutputController> controller = new AudioOutputController(
       event_handler, 0, sync_reader);
 
-  controller->message_loop_ =
-      AudioManager::GetAudioManager()->GetMessageLoop();
-  controller->message_loop_->PostTask(
+  // Start the audio controller thread and post a task to create the
+  // audio stream.
+  controller->thread_.Start();
+  controller->thread_.message_loop()->PostTask(
       FROM_HERE,
       NewRunnableMethod(controller.get(), &AudioOutputController::DoCreate,
                         format, channels, sample_rate, bits_per_sample,
@@ -108,43 +108,43 @@ scoped_refptr<AudioOutputController> AudioOutputController::CreateLowLatency(
 }
 
 void AudioOutputController::Play() {
-  DCHECK(message_loop_);
-  message_loop_->PostTask(
+  DCHECK(thread_.IsRunning());
+  thread_.message_loop()->PostTask(
       FROM_HERE,
       NewRunnableMethod(this, &AudioOutputController::DoPlay));
 }
 
 void AudioOutputController::Pause() {
-  DCHECK(message_loop_);
-  message_loop_->PostTask(
+  DCHECK(thread_.IsRunning());
+  thread_.message_loop()->PostTask(
       FROM_HERE,
       NewRunnableMethod(this, &AudioOutputController::DoPause));
 }
 
 void AudioOutputController::Flush() {
-  DCHECK(message_loop_);
-  message_loop_->PostTask(
+  DCHECK(thread_.IsRunning());
+  thread_.message_loop()->PostTask(
       FROM_HERE,
       NewRunnableMethod(this, &AudioOutputController::DoFlush));
 }
 
 void AudioOutputController::Close() {
-  {
-    AutoLock auto_lock(lock_);
-    // Don't do anything if the stream is already closed.
-    if (state_ == kClosed)
-      return;
-    state_ = kClosed;
+  if (!thread_.IsRunning()) {
+    // If the thread is not running make sure we are stopped.
+    DCHECK_EQ(kClosed, state_);
+    return;
   }
 
-  message_loop_->PostTask(
+  // Wait for all tasks to complete on the audio thread.
+  thread_.message_loop()->PostTask(
       FROM_HERE,
       NewRunnableMethod(this, &AudioOutputController::DoClose));
+  thread_.Stop();
 }
 
 void AudioOutputController::SetVolume(double volume) {
-  DCHECK(message_loop_);
-  message_loop_->PostTask(
+  DCHECK(thread_.IsRunning());
+  thread_.message_loop()->PostTask(
       FROM_HERE,
       NewRunnableMethod(this, &AudioOutputController::DoSetVolume, volume));
 }
@@ -159,14 +159,8 @@ void AudioOutputController::EnqueueData(const uint8* data, uint32 size) {
 void AudioOutputController::DoCreate(AudioManager::Format format, int channels,
                                      int sample_rate, int bits_per_sample,
                                      uint32 hardware_buffer_size) {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
-
-  AutoLock auto_lock(lock_);
-
-  // Close() can be called before DoCreate() is executed.
-  if (state_ == kClosed)
-    return;
-  DCHECK(state_ == kEmpty);
+  DCHECK_EQ(thread_.message_loop(), MessageLoop::current());
+  DCHECK_EQ(kEmpty, state_);
 
   // Create the stream in the first place.
   stream_ = AudioManager::GetAudioManager()->MakeAudioOutputStream(
@@ -197,20 +191,22 @@ void AudioOutputController::DoCreate(AudioManager::Format format, int channels,
 
   // If in normal latency mode then start buffering.
   if (!LowLatencyMode()) {
+    AutoLock auto_lock(lock_);
     SubmitOnMoreData_Locked();
   }
 }
 
 void AudioOutputController::DoPlay() {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(thread_.message_loop(), MessageLoop::current());
+
+  // We can start from created or paused state.
+  if (state_ != kCreated && state_ != kPaused)
+    return;
 
   State old_state;
   // Update the |state_| to kPlaying.
   {
     AutoLock auto_lock(lock_);
-    // We can start from created or paused state.
-    if (state_ != kCreated && state_ != kPaused)
-      return;
     old_state = state_;
     state_ = kPlaying;
   }
@@ -223,14 +219,15 @@ void AudioOutputController::DoPlay() {
 }
 
 void AudioOutputController::DoPause() {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(thread_.message_loop(), MessageLoop::current());
+
+  // We can pause from started state.
+  if (state_ != kPlaying)
+    return;
 
   // Sets the |state_| to kPaused so we don't draw more audio data.
   {
     AutoLock auto_lock(lock_);
-    // We can pause from started state.
-    if (state_ != kPlaying)
-      return;
     state_ = kPaused;
   }
 
@@ -243,22 +240,24 @@ void AudioOutputController::DoPause() {
 }
 
 void AudioOutputController::DoFlush() {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(thread_.message_loop(), MessageLoop::current());
+
+  if (state_ != kPaused)
+    return;
 
   // TODO(hclam): Actually flush the audio device.
 
   // If we are in the regular latency mode then flush the push source.
   if (!sync_reader_) {
     AutoLock auto_lock(lock_);
-    if (state_ != kPaused)
-      return;
     push_source_.ClearAll();
   }
 }
 
 void AudioOutputController::DoClose() {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
-  DCHECK_EQ(kClosed, state_);
+  DCHECK_EQ(thread_.message_loop(), MessageLoop::current());
+  DCHECK_NE(kClosed, state_);
+
   // |stream_| can be null if creating the device failed in DoCreate().
   if (stream_) {
     stream_->Stop();
@@ -266,26 +265,27 @@ void AudioOutputController::DoClose() {
     // After stream is closed it is destroyed, so don't keep a reference to it.
     stream_ = NULL;
   }
+
+  // Update the current state. Since the stream is closed at this point
+  // there's no other threads reading |state_| so we don't need to lock.
+  state_ = kClosed;
 }
 
 void AudioOutputController::DoSetVolume(double volume) {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(thread_.message_loop(), MessageLoop::current());
 
   // Saves the volume to a member first. We may not be able to set the volume
   // right away but when the stream is created we'll set the volume.
   volume_ = volume;
 
-  {
-    AutoLock auto_lock(lock_);
-    if (state_ != kPlaying && state_ != kPaused && state_ != kCreated)
-      return;
-  }
+  if (state_ != kPlaying && state_ != kPaused && state_ != kCreated)
+    return;
 
   stream_->SetVolume(volume_);
 }
 
 void AudioOutputController::DoReportError(int code) {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(thread_.message_loop(), MessageLoop::current());
   handler_->OnError(this, code);
 }
 
@@ -332,7 +332,7 @@ void AudioOutputController::OnClose(AudioOutputStream* stream) {
 
 void AudioOutputController::OnError(AudioOutputStream* stream, int code) {
   // Handle error on the audio controller thread.
-  message_loop_->PostTask(
+  thread_.message_loop()->PostTask(
       FROM_HERE,
       NewRunnableMethod(this, &AudioOutputController::DoReportError, code));
 }
diff --git a/media/audio/audio_output_controller.h b/media/audio/audio_output_controller.h
index 4600067..10e3d03 100644
--- a/media/audio/audio_output_controller.h
+++ b/media/audio/audio_output_controller.h
@@ -8,13 +8,11 @@
 #include "base/lock.h"
 #include "base/ref_counted.h"
 #include "base/scoped_ptr.h"
+#include "base/thread.h"
 #include "base/time.h"
 #include "media/audio/audio_io.h"
-#include "media/audio/audio_manager.h"
 #include "media/audio/simple_sources.h"
 
-class MessageLoop;
-
 // An AudioOutputController controls an AudioOutputStream and provides data
 // to this output stream. It has an important function that it executes
 // audio operations like play, pause, stop, etc. on a separate thread,
@@ -140,9 +138,9 @@ class AudioOutputController
   // has effect when the stream is paused.
   void Flush();
 
-  // Closes the audio output stream. It changes state to kClosed and returns
-  // right away. The physical resources are freed on the audio thread if
-  // neccessary.
+  // Closes the audio output stream and shutdown the audio controller thread.
+  // This method returns only after all operations are completed. This
+  // controller cannot be used after this method is called.
   //
   // It is safe to call this method more than once. Calls after the first one
   // will have no effect.
@@ -205,8 +203,8 @@ class AudioOutputController
   // SyncReader is used only in low latency mode for synchronous reading.
   SyncReader* sync_reader_;
 
-  // The message loop of audio thread that this object runs on.
-  MessageLoop* message_loop_;
+  // The audio controller thread that this object runs on.
+  base::Thread thread_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputController);
 };
diff --git a/media/audio/audio_output_controller_unittest.cc b/media/audio/audio_output_controller_unittest.cc
index df96f4a..a68571a 100644
--- a/media/audio/audio_output_controller_unittest.cc
+++ b/media/audio/audio_output_controller_unittest.cc
@@ -14,7 +14,6 @@ using ::testing::AtLeast;
 using ::testing::Exactly;
 using ::testing::InvokeWithoutArgs;
 using ::testing::NotNull;
-using ::testing::Return;
 
 static const int kSampleRate = AudioManager::kAudioCDSampleRate;
 static const int kBitsPerSample = 16;
@@ -69,10 +68,6 @@ static bool IsRunningHeadless() {
   return false;
 }
 
-ACTION_P(SignalEvent, event) {
-  event->Signal();
-}
-
 ACTION_P3(SignalEvent, event, count, limit) {
   if (++*count >= limit) {
     event->Signal();
@@ -91,10 +86,7 @@ TEST(AudioOutputControllerTest, CreateAndClose) {
                                     kHardwareBufferSize, kBufferCapacity);
   ASSERT_TRUE(controller.get());
 
-  // Close the controller immediately. At this point, chances are that
-  // DoCreate() hasn't been called yet. In any case, it should be safe to call
-  // Close() and it should not try to call |event_handler| later (the test
-  // would crash otherwise).
+  // Close the controller immediately.
   controller->Close();
 }
 
@@ -108,7 +100,7 @@ TEST(AudioOutputControllerTest, PlayAndClose) {
 
   // If OnCreated is called then signal the event.
   EXPECT_CALL(event_handler, OnCreated(NotNull()))
-      .WillOnce(SignalEvent(&event));
+      .WillOnce(InvokeWithoutArgs(&event, &base::WaitableEvent::Signal));
 
   // OnPlaying() will be called only once.
   EXPECT_CALL(event_handler, OnPlaying(NotNull()))
@@ -128,13 +120,14 @@ TEST(AudioOutputControllerTest, PlayAndClose) {
 
   // Wait for OnCreated() to be called.
   event.Wait();
+  event.Reset();
 
   // Play and then wait for the event to be signaled.
   controller->Play();
   event.Wait();
 
-  // Now stop the controller. The object is freed later after DoClose() is
-  // executed.
+  // Now stop the controller. This should shutdown the internal
+  // thread and we hold the only reference to it.
   controller->Close();
 }
 
@@ -185,8 +178,8 @@ TEST(AudioOutputControllerTest, PlayPauseClose) {
   controller->Pause();
   event.Wait();
 
-  // Now stop the controller. The object is freed later after DoClose() is
-  // executed.
+  // Now stop the controller. This should shutdown the internal
+  // thread and we hold the only reference to it.
   controller->Close();
 }
 
@@ -249,8 +242,8 @@ TEST(AudioOutputControllerTest, PlayPausePlay) {
   controller->Play();
   event.Wait();
 
-  // Now stop the controller. The object is freed later after DoClose() is
-  // executed.
+  // Now stop the controller. This should shutdown the internal
+  // thread and we hold the only reference to it.
   controller->Close();
 }
 
@@ -277,17 +270,6 @@ TEST(AudioOutputControllerTest, CloseTwice) {
     return;
 
   MockAudioOutputControllerEventHandler event_handler;
-  base::WaitableEvent event(false, false);
-
-  // If OnCreated is called then signal the event.
-  EXPECT_CALL(event_handler, OnCreated(NotNull()))
-      .WillOnce(SignalEvent(&event));
-
-  // One OnMoreData() is expected.
-  EXPECT_CALL(event_handler, OnMoreData(NotNull(), _, 0))
-      .Times(AtLeast(1))
-      .WillRepeatedly(SignalEvent(&event));
-
   scoped_refptr<AudioOutputController> controller =
       AudioOutputController::Create(&event_handler,
                                     AudioManager::AUDIO_PCM_LINEAR, kChannels,
@@ -295,12 +277,7 @@ TEST(AudioOutputControllerTest, CloseTwice) {
                                     kHardwareBufferSize, kBufferCapacity);
   ASSERT_TRUE(controller.get());
 
-  // Wait for OnCreated() to be called.
-  event.Wait();
-
-  // Wait for OnMoreData() to be called.
-  event.Wait();
-
+  // Close the controller immediately.
   controller->Close();
   controller->Close();
 }
diff --git a/media/audio/fake_audio_input_stream_unittest.cc b/media/audio/fake_audio_input_stream_unittest.cc
index 473ed10..16e86a4 100644
--- a/media/audio/fake_audio_input_stream_unittest.cc
+++ b/media/audio/fake_audio_input_stream_unittest.cc
@@ -5,7 +5,6 @@
 #include "base/basictypes.h"
 #include "base/platform_thread.h"
 #include "media/audio/audio_io.h"
-#include "media/audio/audio_manager.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -49,3 +48,4 @@ TEST(FakeAudioInputTest, BasicCallbacks) {
   stream->Stop();
   stream->Close();
 }
+
diff --git a/media/audio/linux/alsa_output.cc b/media/audio/linux/alsa_output.cc
index e8ebc5c..1358dc3 100644
--- a/media/audio/linux/alsa_output.cc
+++ b/media/audio/linux/alsa_output.cc
@@ -376,7 +376,7 @@ void AlsaPcmOutputStream::GetVolume(double* volume) {
 }
 
 void AlsaPcmOutputStream::OpenTask(uint32 packet_size) {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
 
   // Initialize the configuration variables.
   packet_size_ = packet_size;
@@ -422,7 +422,7 @@ void AlsaPcmOutputStream::OpenTask(uint32 packet_size) {
 }
 
 void AlsaPcmOutputStream::StartTask() {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
 
   if (stop_stream_) {
     return;
@@ -454,7 +454,7 @@ void AlsaPcmOutputStream::StartTask() {
 void AlsaPcmOutputStream::CloseTask() {
   // NOTE: Keep this function idempotent to handle errors that might cause
   // multiple CloseTasks to be posted.
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
 
   // Shutdown the audio device.
   if (playback_handle_ && !CloseDevice(playback_handle_)) {
@@ -470,7 +470,7 @@ void AlsaPcmOutputStream::CloseTask() {
 }
 
 void AlsaPcmOutputStream::BufferPacket(bool* source_exhausted) {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
 
   // If stopped, simulate a 0-lengthed packet.
   if (stop_stream_) {
@@ -558,7 +558,7 @@ void AlsaPcmOutputStream::BufferPacket(bool* source_exhausted) {
 }
 
 void AlsaPcmOutputStream::WritePacket() {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
 
   // If the device is in error, just eat the bytes.
   if (stop_stream_) {
@@ -611,7 +611,7 @@ void AlsaPcmOutputStream::WritePacket() {
 }
 
 void AlsaPcmOutputStream::WriteTask() {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
 
   if (stop_stream_) {
     return;
@@ -625,7 +625,7 @@ void AlsaPcmOutputStream::WriteTask() {
 }
 
 void AlsaPcmOutputStream::ScheduleNextWrite(bool source_exhausted) {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
 
   if (stop_stream_) {
     return;
@@ -778,7 +778,7 @@ bool AlsaPcmOutputStream::CloseDevice(snd_pcm_t* handle) {
 }
 
 snd_pcm_sframes_t AlsaPcmOutputStream::GetAvailableFrames() {
-  DCHECK_EQ(message_loop_, MessageLoop::current());
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
 
   if (stop_stream_) {
     return 0;
diff --git a/media/audio/linux/alsa_output.h b/media/audio/linux/alsa_output.h
index f98f2c0..0fb5ac5 100644
--- a/media/audio/linux/alsa_output.h
+++ b/media/audio/linux/alsa_output.h
@@ -36,8 +36,8 @@
 #include "base/lock.h"
 #include "base/ref_counted.h"
 #include "base/scoped_ptr.h"
+#include "base/thread.h"
 #include "media/audio/audio_io.h"
-#include "media/audio/audio_manager_base.h"
 
 namespace media {
 class SeekableBuffer;
diff --git a/media/audio/linux/audio_manager_linux.cc b/media/audio/linux/audio_manager_linux.cc
index 713a753..17a1f74 100644
--- a/media/audio/linux/audio_manager_linux.cc
+++ b/media/audio/linux/audio_manager_linux.cc
@@ -4,6 +4,7 @@
 
 #include "media/audio/linux/audio_manager_linux.h"
 
+#include "base/at_exit.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "media/audio/fake_audio_input_stream.h"
@@ -12,6 +13,12 @@
 #include "media/audio/linux/alsa_wrapper.h"
 #include "media/base/media_switches.h"
 
+
+namespace {
+
+AudioManagerLinux* g_audio_manager = NULL;
+}  // namespace
+
 // Implementation of AudioManager.
 bool AudioManagerLinux::HasAudioOutputDevices() {
   // TODO(ajwong): Make this actually query audio devices.
@@ -49,7 +56,7 @@ AudioOutputStream* AudioManagerLinux::MakeAudioOutputStream(
     return FakeAudioOutputStream::MakeFakeStream();
   }
 
-  if (!initialized()) {
+  if (!initialized_) {
     return NULL;
   }
 
@@ -61,14 +68,16 @@ AudioOutputStream* AudioManagerLinux::MakeAudioOutputStream(
   AlsaPcmOutputStream* stream =
       new AlsaPcmOutputStream(device_name, format, channels, sample_rate,
                               bits_per_sample, wrapper_.get(), this,
-                              GetMessageLoop());
+                              audio_thread_.message_loop());
 
   AutoLock l(lock_);
   active_streams_[stream] = scoped_refptr<AlsaPcmOutputStream>(stream);
   return stream;
 }
 
-AudioManagerLinux::AudioManagerLinux() {
+AudioManagerLinux::AudioManagerLinux()
+    : audio_thread_("AudioThread"),
+      initialized_(false) {
 }
 
 AudioManagerLinux::~AudioManagerLinux() {
@@ -82,7 +91,7 @@ AudioManagerLinux::~AudioManagerLinux() {
 }
 
 void AudioManagerLinux::Init() {
-  AudioManagerBase::Init();
+  initialized_ = audio_thread_.Start();
   wrapper_.reset(new AlsaWrapper());
 }
 
@@ -101,7 +110,17 @@ void AudioManagerLinux::ReleaseOutputStream(AlsaPcmOutputStream* stream) {
   }
 }
 
-// static
-AudioManager* AudioManager::CreateAudioManager() {
-  return new AudioManagerLinux();
+// TODO(ajwong): Collapse this with the windows version.
+void DestroyAudioManagerLinux(void* not_used) {
+  delete g_audio_manager;
+  g_audio_manager = NULL;
+}
+
+AudioManager* AudioManager::GetAudioManager() {
+  if (!g_audio_manager) {
+    g_audio_manager = new AudioManagerLinux();
+    g_audio_manager->Init();
+    base::AtExitManager::RegisterCallback(&DestroyAudioManagerLinux, NULL);
+  }
+  return g_audio_manager;
 }
diff --git a/media/audio/linux/audio_manager_linux.h b/media/audio/linux/audio_manager_linux.h
index 2703eed..ea335f0 100644
--- a/media/audio/linux/audio_manager_linux.h
+++ b/media/audio/linux/audio_manager_linux.h
@@ -11,12 +11,12 @@
 #include "base/ref_counted.h"
 #include "base/scoped_ptr.h"
 #include "base/thread.h"
-#include "media/audio/audio_manager_base.h"
+#include "media/audio/audio_io.h"
 
 class AlsaPcmOutputStream;
 class AlsaWrapper;
 
-class AudioManagerLinux : public AudioManagerBase {
+class AudioManagerLinux : public AudioManager {
  public:
   AudioManagerLinux();
 
@@ -44,12 +44,17 @@ class AudioManagerLinux : public AudioManagerBase {
   virtual ~AudioManagerLinux();
 
  private:
+  // Thread used to interact with AudioOutputStreams created by this
+  // audio manger.
+  base::Thread audio_thread_;
   scoped_ptr<AlsaWrapper> wrapper_;
 
   Lock lock_;
   std::map<AlsaPcmOutputStream*, scoped_refptr<AlsaPcmOutputStream> >
       active_streams_;
 
+  bool initialized_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioManagerLinux);
 };
 
diff --git a/media/audio/mac/audio_manager_mac.cc b/media/audio/mac/audio_manager_mac.cc
index 528fd6e..312ecbb 100644
--- a/media/audio/mac/audio_manager_mac.cc
+++ b/media/audio/mac/audio_manager_mac.cc
@@ -4,6 +4,7 @@
 
 #include <CoreAudio/AudioHardware.h>
 
+#include "base/at_exit.h"
 #include "media/audio/fake_audio_input_stream.h"
 #include "media/audio/fake_audio_output_stream.h"
 #include "media/audio/mac/audio_manager_mac.h"
@@ -74,7 +75,22 @@ void AudioManagerMac::ReleaseOutputStream(
   delete stream;
 }
 
-// static
-AudioManager* AudioManager::CreateAudioManager() {
-  return new AudioManagerMac();
+namespace {
+
+AudioManagerMac* g_audio_manager = NULL;
+
+}  // namespace.
+
+void DestroyAudioManagerMac(void* param) {
+  delete g_audio_manager;
+  g_audio_manager = NULL;
+}
+
+// By convention, the AudioManager is not thread safe.
+AudioManager* AudioManager::GetAudioManager() {
+  if (!g_audio_manager) {
+    g_audio_manager = new AudioManagerMac();
+    base::AtExitManager::RegisterCallback(&DestroyAudioManagerMac, NULL);
+  }
+  return g_audio_manager;
 }
diff --git a/media/audio/mac/audio_manager_mac.h b/media/audio/mac/audio_manager_mac.h
index fa25ece..c05e092 100644
--- a/media/audio/mac/audio_manager_mac.h
+++ b/media/audio/mac/audio_manager_mac.h
@@ -6,14 +6,14 @@
 #define MEDIA_AUDIO_MAC_AUDIO_MANAGER_MAC_H_
 
 #include "base/basictypes.h"
-#include "media/audio/audio_manager_base.h"
+#include "media/audio/audio_io.h"
 
 class PCMQueueOutAudioOutputStream;
 
 // Mac OS X implementation of the AudioManager singleton. This class is internal
 // to the audio output and only internal users can call methods not exposed by
 // the AudioManager class.
-class AudioManagerMac : public AudioManagerBase {
+class AudioManagerMac : public AudioManager {
  public:
   AudioManagerMac() {};
 
diff --git a/media/audio/openbsd/audio_manager_openbsd.cc b/media/audio/openbsd/audio_manager_openbsd.cc
index c2c7b98..7d7a249 100644
--- a/media/audio/openbsd/audio_manager_openbsd.cc
+++ b/media/audio/openbsd/audio_manager_openbsd.cc
@@ -4,6 +4,7 @@
 
 #include "media/audio/openbsd/audio_manager_openbsd.h"
 
+#include "base/at_exit.h"
 #include "base/logging.h"
 
 namespace {
@@ -47,7 +48,6 @@ AudioManagerOpenBSD::~AudioManagerOpenBSD() {
 }
 
 void AudioManagerOpenBSD::Init() {
-  AudioManagerBase::Init();
 }
 
 void AudioManagerOpenBSD::MuteAll() {
@@ -71,8 +71,3 @@ AudioManager* AudioManager::GetAudioManager() {
   }
   return g_audio_manager;
 }
-
-// static
-AudioManager* AudioManager::CreateAudioManager() {
-  return new AudioManagerOpenBSD();
-}
diff --git a/media/audio/openbsd/audio_manager_openbsd.h b/media/audio/openbsd/audio_manager_openbsd.h
index fc35a37..ddbce23 100644
--- a/media/audio/openbsd/audio_manager_openbsd.h
+++ b/media/audio/openbsd/audio_manager_openbsd.h
@@ -7,7 +7,7 @@
 
 #include "media/audio/audio_io.h"
 
-class AudioManagerOpenBSD : public AudioManagerBase {
+class AudioManagerOpenBSD : public AudioManager {
  public:
   AudioManagerOpenBSD();
 
diff --git a/media/audio/simple_sources_unittest.cc b/media/audio/simple_sources_unittest.cc
index 029d565..7ddc23f 100644
--- a/media/audio/simple_sources_unittest.cc
+++ b/media/audio/simple_sources_unittest.cc
@@ -6,7 +6,6 @@
 #include "base/basictypes.h"
 #include "base/scoped_ptr.h"
 #include "base/time.h"
-#include "media/audio/audio_manager.h"
 #include "media/audio/fake_audio_output_stream.h"
 #include "media/audio/simple_sources.h"
 #include "testing/gtest/include/gtest/gtest.h"
diff --git a/media/audio/win/audio_manager_win.cc b/media/audio/win/audio_manager_win.cc
index 6c4a606..061d2d8 100644
--- a/media/audio/win/audio_manager_win.cc
+++ b/media/audio/win/audio_manager_win.cc
@@ -7,6 +7,7 @@
 #include <windows.h>
 #include <mmsystem.h>
 
+#include "base/at_exit.h"
 #include "base/basictypes.h"
 #include "media/audio/fake_audio_input_stream.h"
 #include "media/audio/fake_audio_output_stream.h"
@@ -41,6 +42,8 @@ const int kMaxSamplesPerPacket = kMaxSampleRate;
 // play.
 const int kNumInputBuffers = 3;
 
+AudioManagerWin* g_audio_manager = NULL;
+
 }  // namespace.
 
 bool AudioManagerWin::HasAudioOutputDevices() {
@@ -122,7 +125,15 @@ void AudioManagerWin::UnMuteAll() {
 AudioManagerWin::~AudioManagerWin() {
 }
 
-// static
-AudioManager* AudioManager::CreateAudioManager() {
-  return new AudioManagerWin();
+void DestroyAudioManagerWin(void* param) {
+  delete g_audio_manager;
+  g_audio_manager = NULL;
+}
+
+AudioManager* AudioManager::GetAudioManager() {
+  if (!g_audio_manager) {
+    g_audio_manager = new AudioManagerWin();
+    base::AtExitManager::RegisterCallback(&DestroyAudioManagerWin, NULL);
+  }
+  return g_audio_manager;
 }
diff --git a/media/audio/win/audio_manager_win.h b/media/audio/win/audio_manager_win.h
index b8bd579..21a4014 100644
--- a/media/audio/win/audio_manager_win.h
+++ b/media/audio/win/audio_manager_win.h
@@ -8,7 +8,7 @@
 #include <windows.h>
 
 #include "base/basictypes.h"
-#include "media/audio/audio_manager_base.h"
+#include "media/audio/audio_io.h"
 
 class PCMWaveInAudioInputStream;
 class PCMWaveOutAudioOutputStream;
@@ -16,7 +16,7 @@ class PCMWaveOutAudioOutputStream;
 // Windows implementation of the AudioManager singleton. This class is internal
 // to the audio output and only internal users can call methods not exposed by
 // the AudioManager class.
-class AudioManagerWin : public AudioManagerBase {
+class AudioManagerWin : public AudioManager {
  public:
   AudioManagerWin() {}
   // Implementation of AudioManager.
diff --git a/media/filters/audio_renderer_impl.cc b/media/filters/audio_renderer_impl.cc
index 9fd1034..0f4a053 100644
--- a/media/filters/audio_renderer_impl.cc
+++ b/media/filters/audio_renderer_impl.cc
@@ -7,7 +7,6 @@
 #include <math.h>
 
 #include "media/base/filter_host.h"
-#include "media/audio/audio_manager.h"
 
 namespace media {
 
diff --git a/media/media.gyp b/media/media.gyp
index eec7678..45815e72 100644
--- a/media/media.gyp
+++ b/media/media.gyp
@@ -23,10 +23,6 @@
         'audio/audio_io.h',
         'audio/audio_input_controller.cc',
         'audio/audio_input_controller.h',
-        'audio/audio_manager.h',
-        'audio/audio_manager.cc',
-        'audio/audio_manager_base.h',
-        'audio/audio_manager_base.cc',
         'audio/audio_output_controller.cc',
         'audio/audio_output_controller.h',
         'audio/audio_util.cc',