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 b024d9fc7fee9e5b5d2526a2c8c5017db6a3d118..c5730ea8a3d3869f85b66d99b9bdf32d0737be78 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -51,7 +51,6 @@
 #include "components/tracing/common/trace_config_file.h"
 #include "components/tracing/common/trace_to_console.h"
 #include "components/tracing/common/tracing_switches.h"
-#include "content/browser/audio_manager_thread.h"
 #include "content/browser/browser_thread_impl.h"
 #include "content/browser/dom_storage/dom_storage_area.h"
 #include "content/browser/download/download_resource_handler.h"
@@ -91,7 +90,9 @@
 #include "content/public/common/result_codes.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/audio/audio_thread_impl.h"
 #include "media/base/media.h"
 #include "media/base/user_input_monitor.h"
 #include "media/midi/midi_service.h"
@@ -1354,6 +1355,10 @@ 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");
@@ -1744,15 +1749,13 @@ void BrowserMainLoop::EndStartupTracing() {
 }
 
 void BrowserMainLoop::CreateAudioManager() {
-  DCHECK(!audio_thread_);
   DCHECK(!audio_manager_);
 
   audio_manager_ = GetContentClient()->browser()->CreateAudioManager(
       MediaInternals::GetInstance());
   if (!audio_manager_) {
-    audio_thread_ = base::MakeUnique<AudioManagerThread>();
     audio_manager_ = media::AudioManager::Create(
-        audio_thread_->task_runner(), audio_thread_->worker_task_runner(),
+        base::MakeUnique<media::AudioThreadImpl>(),
         BrowserThread::GetTaskRunnerForThread(BrowserThread::FILE),
         MediaInternals::GetInstance());
   }
@@ -1762,4 +1765,13 @@ void BrowserMainLoop::CreateAudioManager() {
   CHECK(audio_system_);
 }
 
+void BrowserMainLoop::DestroyAudioManager() {
+  DCHECK(audio_manager_);
+
+  audio_system_.reset();

[o1ka, 2017/04/28 13:24:19]

Audio thread can have AudioSystem operations posted to it, and now they refer to
an invalid pointer.

Should we fix it according to the decision in the mail thread?

1. AudioManager::Shutdown(): This shuts down the AudioManager and stops the
audio thread.
2. delete AudioSystem
3. delete AudioThread
4. delete AudioManager

[alokp, 2017/04/28 17:31:12]

Good catch. IMO we should just shutdown the AM here and let ~BML destroy
AudioSystem and AudioManager in correct order. WDYT?

[o1ka, 2017/05/02 16:16:00]

sgtm

[alokp, 2017/05/09 19:06:15]

Done.

+
+  audio_manager_->Shutdown();
+  audio_manager_.reset();
+}
+
 }  // namespace content