Fix InitializeOnAudioThread race.

It may race with ShutdownOnAudioThread when running the audio service
out of process.

Bug: 854816
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I2ccd4254f4c4f0f70ffb2180c3a586e35ce1baed
Reviewed-on: https://chromium-review.googlesource.com/1109683Reviewed-by: Henrik Grunell <grunell@chromium.org>
Commit-Queue: Max Morin <maxmorin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570029}

media/audio/mac/audio_manager_mac.cc

@@ -504,15 +504,15 @@ AudioManagerMac::AudioManagerMac(std::unique_ptr<AudioThread> audio_thread,
     : AudioManagerBase(std::move(audio_thread), audio_log_factory),
       current_sample_rate_(0),
       current_output_device_(kAudioDeviceUnknown),
-      in_shutdown_(false) {
+      in_shutdown_(false),
+      weak_ptr_factory_(this) {
   SetMaxOutputStreamsAllowed(kMaxOutputStreams);
 
-  // Task must be posted last to avoid races from handing out "this" to the
-  // audio thread.  Always PostTask even if we're on the right thread since
-  // AudioManager creation is on the startup path and this may be slow.
+  // PostTask since AudioManager creation may be on the startup path and this
+  // may be slow.
   GetTaskRunner()->PostTask(
       FROM_HERE, base::Bind(&AudioManagerMac::InitializeOnAudioThread,
-                            base::Unretained(this)));
+                            weak_ptr_factory_.GetWeakPtr()));
 }
 
 AudioManagerMac::~AudioManagerMac() = default;

media/audio/mac/audio_manager_mac.h

@@ -16,6 +16,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "media/audio/audio_manager_base.h"
 #include "media/audio/mac/audio_device_listener_mac.h"
 
@@ -215,6 +216,8 @@ class MEDIA_EXPORT AudioManagerMac : public AudioManagerBase {
   // Core Audio APIs are not executed during shutdown.
   bool in_shutdown_;
 
+  base::WeakPtrFactory<AudioManagerMac> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioManagerMac);
 };
 

media/audio/win/audio_manager_win.cc

@@ -92,12 +92,20 @@ AudioManagerWin::AudioManagerWin(std::unique_ptr<AudioThread> audio_thread,
 
   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.
+  // WARNING: This may be 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.
+
+  // In case we are already on the audio thread (i.e. when running out of
+  // process audio), don't post.
+  if (GetTaskRunner()->BelongsToCurrentThread()) {
+    this->InitializeOnAudioThread();
+    return;
+  }
 
   // Task must be posted last to avoid races from handing out "this" to the
-  // audio thread.
+  // audio thread. Unretained is safe since we join the audio thread before
+  // destructing |this|.
   GetTaskRunner()->PostTask(
       FROM_HERE, base::Bind(&AudioManagerWin::InitializeOnAudioThread,
                             base::Unretained(this)));