Allow blocking when audio::OutputDevice joins the audio thread.

BUG=858987

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: Ic61830a546ffe6873fef4db18a49d03031293fe7
Reviewed-on: https://chromium-review.googlesource.com/1119914Reviewed-by: Marina Ciocea <marinaciocea@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Max Morin <maxmorin@chromium.org>
Commit-Queue: Olga Sharonova <olka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577832}

base/threading/thread_restrictions.h

@@ -20,7 +20,9 @@ class AwFormDatabaseService;
 class CookieManager;
 class ScopedAllowInitGLBindings;
 }
-
+namespace audio {
+class OutputDevice;
+}
 namespace cc {
 class CompletionEvent;
 class SingleThreadTaskGraphRunner;
@@ -249,6 +251,7 @@ class BASE_EXPORT ScopedAllowBlocking {
   // in unit tests to avoid the friend requirement.
   FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest, ScopedAllowBlocking);
   friend class android_webview::ScopedAllowInitGLBindings;
+  friend class audio::OutputDevice;
   friend class content::BrowserProcessSubThread;
   friend class content::GpuProcessTransportFactory;
   friend class cronet::CronetPrefsManager;

media/audio/audio_device_thread.h

@@ -72,6 +72,7 @@ class MEDIA_EXPORT AudioDeviceThread : public base::PlatformThread::Delegate {
 
   // This tells the audio thread to stop and clean up the data; this is a
   // synchronous process and the thread will stop before the method returns.
+  // Blocking call, see base/threading/thread_restrictions.h.
   ~AudioDeviceThread() override;
 
  private:

services/audio/public/cpp/output_device.cc

@@ -6,6 +6,7 @@
 
 #include <utility>
 
+#include "base/threading/thread_restrictions.h"
 #include "media/audio/audio_output_device_thread_callback.h"
 #include "mojo/public/cpp/system/platform_handle.h"
 #include "services/audio/public/mojom/constants.mojom.h"
@@ -27,8 +28,8 @@ OutputDevice::OutputDevice(
 
   media::mojom::AudioOutputStreamRequest stream_request =
       mojo::MakeRequest(&stream_);
-  stream_.set_connection_error_handler(
-      base::BindOnce(&OutputDevice::CleanUp, weak_factory_.GetWeakPtr()));
+  stream_.set_connection_error_handler(base::BindOnce(
+      &OutputDevice::OnConnectionError, weak_factory_.GetWeakPtr()));
   stream_factory_->CreateOutputStream(
       std::move(stream_request), nullptr, nullptr, device_id, params,
       base::UnguessableToken::Create(),
@@ -68,16 +69,25 @@ void OutputDevice::StreamCreated(
       data_pipe->shared_memory;
   DCHECK(shared_memory_region.IsValid());
 
-  audio_callback_.reset(new media::AudioOutputDeviceThreadCallback(
-      audio_parameters_, std::move(shared_memory_region), render_callback_));
-  audio_thread_.reset(new media::AudioDeviceThread(
+  DCHECK(!audio_callback_);
+  DCHECK(!audio_thread_);
+  audio_callback_ = std::make_unique<media::AudioOutputDeviceThreadCallback>(
+      audio_parameters_, std::move(shared_memory_region), render_callback_);
+  audio_thread_ = std::make_unique<media::AudioDeviceThread>(
       audio_callback_.get(), socket_handle, "audio::OutputDevice",
-      base::ThreadPriority::REALTIME_AUDIO));
+      base::ThreadPriority::REALTIME_AUDIO);
+}
+
+void OutputDevice::OnConnectionError() {
+  // Connection errors should be rare and handling them synchronously is
+  // simpler.
+  base::ScopedAllowBlocking allow_blocking;
+  CleanUp();
 }
 
 void OutputDevice::CleanUp() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
-  audio_thread_.reset();
+  audio_thread_.reset();  // Blocking call.
   audio_callback_.reset();
   stream_.reset();
   stream_factory_.reset();

services/audio/public/cpp/output_device.h

@@ -22,10 +22,13 @@ namespace audio {
 
 class OutputDevice {
  public:
+  // media::AudioRendererSink::RenderCallback must outlive |this|.
   OutputDevice(std::unique_ptr<service_manager::Connector> connector,
                const media::AudioParameters& params,
                media::AudioRendererSink::RenderCallback* callback,
                const std::string& device_id);
+
+  // Blocking call; see base/threading/thread_restrictions.h.
   ~OutputDevice();
 
   void Play();
@@ -34,7 +37,8 @@ class OutputDevice {
 
  private:
   void StreamCreated(media::mojom::ReadWriteAudioDataPipePtr data_pipe);
-  void CleanUp();
+  void OnConnectionError();
+  void CleanUp();  // Blocking call.
 
   SEQUENCE_CHECKER(sequence_checker_);