Ensures that audio tasks cannot run after AudioManager is deleted.

media/audio/win/audio_manager_win.cc

 // Copyright (c) 2012 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/win/audio_manager_win.h"
 
 #include <windows.h>
 #include <objbase.h>  // This has to be before initguid.h
 #include <initguid.h>
 #include <mmsystem.h>
@@ skipping 113 matching lines @@
 
   // Use 4 buffers for Vista, 3 for everyone else:
   //  - The entire Windows audio stack was rewritten for Windows Vista and wave
   //    out performance was degraded compared to XP.
   //  - The regression was fixed in Windows 7 and most configurations will work
   //    with 2, but some (e.g., some Sound Blasters) still need 3.
   //  - Some XP configurations (even multi-processor ones) also need 3.
   return (base::win::GetVersion() == base::win::VERSION_VISTA) ? 4 : 3;
 }
 
-AudioManagerWin::AudioManagerWin(
-    scoped_refptr<base::SingleThreadTaskRunner> task_runner,
-    scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
-    AudioLogFactory* audio_log_factory)
-    : AudioManagerBase(std::move(task_runner),
-                       std::move(worker_task_runner),
-                       audio_log_factory) {
+AudioManagerWin::AudioManagerWin(std::unique_ptr<AudioThread> audio_thread,
+                                 AudioLogFactory* audio_log_factory)
+    : AudioManagerBase(std::move(audio_thread), audio_log_factory) {
   // |CoreAudioUtil::IsSupported()| uses static variables to avoid doing
   // multiple initializations.  This is however not thread safe.
   // So, here we call it explicitly before we kick off the audio thread
   // or do any other work.
   CoreAudioUtil::IsSupported();
 
   SetMaxOutputStreamsAllowed(kMaxOutputStreams);
 
   // WARNING: This is executed on the UI loop, do not add any code here which
   // loads libraries or attempts to call out into the OS.  Instead add such code
   // to the InitializeOnAudioThread() method below.
 
   // Task must be posted last to avoid races from handing out "this" to the
   // audio thread.
   GetTaskRunner()->PostTask(
       FROM_HERE, base::Bind(&AudioManagerWin::InitializeOnAudioThread,
                             base::Unretained(this)));
 }
 
-AudioManagerWin::~AudioManagerWin() {
-  Shutdown();
+AudioManagerWin::~AudioManagerWin() = default;
+
+void AudioManagerWin::ShutdownOnAudioThread() {
+  AudioManagerBase::ShutdownOnAudioThread();
+  output_device_listener_.reset();

[o1ka, 2017/05/10 15:57:57]

Add a comment why it's done here?

[alokp, 2017/05/10 18:04:03]

Done.

 }
 
 bool AudioManagerWin::HasAudioOutputDevices() {
   return (::waveOutGetNumDevs() != 0);
 }
 
 bool AudioManagerWin::HasAudioInputDevices() {
   return (::waveInGetNumDevs() != 0);
 }
 
@@ skipping 285 matching lines @@
   if (user_buffer_size)
     buffer_size = user_buffer_size;
 
   AudioParameters params(AudioParameters::AUDIO_PCM_LOW_LATENCY, channel_layout,
                          sample_rate, bits_per_sample, buffer_size);
   params.set_effects(effects);
   return params;
 }
 
 // static
-ScopedAudioManagerPtr CreateAudioManager(
-    scoped_refptr<base::SingleThreadTaskRunner> task_runner,
-    scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
+std::unique_ptr<AudioManager> CreateAudioManager(
+    std::unique_ptr<AudioThread> audio_thread,
     AudioLogFactory* audio_log_factory) {
-  return ScopedAudioManagerPtr(
-      new AudioManagerWin(std::move(task_runner), std::move(worker_task_runner),
-                          audio_log_factory));
+  return base::MakeUnique<AudioManagerWin>(std::move(audio_thread),
+                                           audio_log_factory);
 }
 
 }  // namespace media