Ensures that audio tasks cannot run after AudioManager is deleted.

content/browser/browser_main_loop.cc

Index: content/browser/browser_main_loop.cc
diff --git a/content/browser/browser_main_loop.cc b/content/browser/browser_main_loop.cc
index 5e96a960c6ce476aa5682fbf51b0b8bcb8069f30..68acd42072e90767de07e2a8c217590a08274107 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -93,6 +93,7 @@
 #include "device/battery/battery_status_service.h"
 #include "device/gamepad/gamepad_service.h"
 #include "gpu/vulkan/features.h"
+#include "media/audio/audio_manager.h"
 #include "media/audio/audio_system_impl.h"
 #include "media/base/media.h"
 #include "media/base/user_input_monitor.h"
@@ -1393,6 +1394,10 @@ void BrowserMainLoop::ShutdownThreadsAndCleanUp() {
     TRACE_EVENT0("shutdown", "BrowserMainLoop::Subsystem:DeleteDataSources");
     URLDataManager::DeleteDataSources();
   }
+  {
+    TRACE_EVENT0("shutdown", "BrowserMainLoop::Subsystem:AudioMan");
+    DestroyAudioManager();
+  }
 
   if (parts_) {
     TRACE_EVENT0("shutdown", "BrowserMainLoop::Subsystem:PostDestroyThreads");
@@ -1781,10 +1786,11 @@ void BrowserMainLoop::CreateAudioManager() {
   DCHECK(!audio_thread_);
   DCHECK(!audio_manager_);
 
+  audio_thread_ = base::MakeUnique<AudioManagerThread>();
   audio_manager_ = GetContentClient()->browser()->CreateAudioManager(
+      audio_thread_->task_runner(), audio_thread_->worker_task_runner(),
       MediaInternals::GetInstance());
   if (!audio_manager_) {
-    audio_thread_ = base::MakeUnique<AudioManagerThread>();
     audio_manager_ = media::AudioManager::Create(
         audio_thread_->task_runner(), audio_thread_->worker_task_runner(),
         BrowserThread::GetTaskRunnerForThread(BrowserThread::FILE),
@@ -1796,4 +1802,25 @@ void BrowserMainLoop::CreateAudioManager() {
   CHECK(audio_system_);
 }
 
+void BrowserMainLoop::DestroyAudioManager() {
+  DCHECK(audio_manager_);
+  DCHECK(audio_thread_);
+
+  // |audio_manager_| must be shut down on |audio_thread_| before it is deleted.
+  if (audio_manager_->GetTaskRunner()->BelongsToCurrentThread()) {
+    audio_manager_->Shutdown();
+  } else {
+    audio_manager_->GetTaskRunner()->PostTask(
+        FROM_HERE, base::Bind(&media::AudioManager::Shutdown,
+                              base::Unretained(audio_manager_.get())));
+  }
+
+  // Stop |audio_thread_| before deleting |audio_manager_| so that all tasks
+  // currently in the |audio_thread_| queue run and no more can be posted.
+  audio_thread_.reset();

[o1ka, 2017/03/28 18:32:23]

Is there a guarantee that all the queued tasks will run? (Sorry cannot look it
up now - I'm on the go)

[o1ka, 2017/03/29 09:28:32]

Never mind - I checked it now, base::Thread will do it :)

+
+  // Safe to delete the |audio_manager_|.
+  audio_manager_.reset();

[o1ka, 2017/03/28 18:32:23]

Looks like we need to reset AudioSystem before this?

+}
+
 }  // namespace content