Pass task runners to AudioManager constructor.

media/audio/audio_manager.cc

Index: media/audio/audio_manager.cc
diff --git a/media/audio/audio_manager.cc b/media/audio/audio_manager.cc
index 5d5f3b3a63337dd1df6fb307a6a17f046529704b..821407c720dc70546761e67284229f4ff8e7c926 100644
--- a/media/audio/audio_manager.cc
+++ b/media/audio/audio_manager.cc
@@ -258,11 +258,15 @@ base::LazyInstance<AudioManagerHelper>::Leaky g_helper =
 // Forward declaration of the platform specific AudioManager factory function.
 AudioManager* CreateAudioManager(AudioLogFactory* audio_log_factory);
 
-AudioManager::AudioManager() {}
+AudioManager::AudioManager(
+    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
+    const scoped_refptr<base::SingleThreadTaskRunner>& worker_task_runner)
+    : task_runner_(task_runner), worker_task_runner_(worker_task_runner) {
+  g_last_created = this;
+}
 
 AudioManager::~AudioManager() {
-  CHECK(!g_last_created || g_last_created == this);
-  g_last_created = nullptr;
+  DCHECK(task_runner_->BelongsToCurrentThread());
 }
 
 // static
@@ -283,13 +287,10 @@ void AudioManager::ResetFactoryForTesting() {
 
 // static
 AudioManager* AudioManager::Create(AudioLogFactory* audio_log_factory) {
-  CHECK(!g_last_created);
   if (g_audio_manager_factory)
-    g_last_created = g_audio_manager_factory->CreateInstance(audio_log_factory);
+    return g_audio_manager_factory->CreateInstance(audio_log_factory);
   else
-    g_last_created = CreateAudioManager(audio_log_factory);
-
-  return g_last_created;
+    return CreateAudioManager(audio_log_factory);
 }
 
 // static
@@ -316,6 +317,27 @@ AudioManager* AudioManager::CreateForTesting() {
 }
 
 // static
+void AudioManager::Destroy(AudioManager* instance) {
+  CHECK(instance);
+  CHECK_EQ(g_last_created, instance);
+
+  // AudioManager must be destroyed on the audio thread.
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner =
+      instance->GetTaskRunner();
+  if (task_runner->BelongsToCurrentThread()) {
+    delete instance;
+  } else {
+    task_runner->DeleteSoon(FROM_HERE, instance);
+  }
+
+  // We reset g_last_created here instead of in the destructor of AudioManager
+  // to allow construction of another AudioManager while the current instance
+  // is being destroyed. This overlap does not happen in production - only in
+  // unittests.
+  g_last_created = nullptr;
+}
+
+// static
 void AudioManager::EnableCrashKeyLoggingForAudioThreadHangs() {
   CHECK(!g_last_created);
   g_helper.Pointer()->enable_crash_key_logging();