Remove the AudioManager singleton.

media/audio/audio_manager.cc

 // Copyright (c) 2011 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"
+#include "base/message_loop.h"
 
-static bool g_destroy_called = false;
+// Used only to make sure we never create more than one instance.

[henrika (OOO until Aug 14), 2011/12/06 16:53:28]

I have read the comment but still don't understand why this global handle is
needed? What type of situation are you protecting us from here?

[tommi (sloooow) - chröme, 2011/12/06 20:28:48]

This is a safeguard to make sure that there exists never more than one instance
of the AudioManager.  This variable is not exposed or used for anything other
than to check if there already exists an instance and catch the programmer error
early.
The checks are in the constructor and destructor.  The check in
AudioManager::Create isn't really necessary, but I put it there in case anyone
would ever return an "AudioManager" that does not derive from the AudioManager
class.

 static AudioManager* g_audio_manager = NULL;
 
-// static
-void AudioManager::Destroy(void* not_used) {
-  g_destroy_called = true;
-
-  if (g_audio_manager) {
-    g_audio_manager->Cleanup();
-
-    AudioManager* audio_manager = g_audio_manager;
-    g_audio_manager = NULL;
-    delete audio_manager;
-  }
+AudioManager::AudioManager() {
+  CHECK(g_audio_manager == NULL);
+  g_audio_manager = this;
 }
 
-// static
-AudioManager* AudioManager::GetAudioManager() {
-  if (!g_audio_manager && !g_destroy_called) {
-    g_audio_manager = CreateAudioManager();
-    g_audio_manager->Init();
-    base::AtExitManager::RegisterCallback(&AudioManager::Destroy, NULL);
-  }
-  return g_audio_manager;
+AudioManager::~AudioManager() {
+  CHECK(g_audio_manager == this);
+  g_audio_manager = NULL;
 }
 
-// static
-bool AudioManager::SingletonExists() {
-  return g_audio_manager != NULL;
+#ifndef NDEBUG
+void AudioManager::AddRef() const {
+  base::RefCountedThreadSafe<AudioManager>::AddRef();
 }
 
+void AudioManager::Release() const {
+  base::RefCountedThreadSafe<AudioManager>::Release();
+}
+#endif
+
 // static
-void AudioManager::Resurrect() {
-  g_destroy_called = false;
+scoped_refptr<AudioManager> AudioManager::Create() {
+  AudioManager* ret = CreateAudioManager();
+  DCHECK(ret == g_audio_manager);
+  ret->Init();
+  return ret;
 }