Ensures that audio tasks cannot run after AudioManager is deleted.

media/audio/audio_thread_impl.cc

+// Copyright 2016 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/audio_thread_impl.h"
+
+#include "base/threading/thread_task_runner_handle.h"
+
+namespace media {
+
+AudioThreadImpl::AudioThreadImpl() : thread_("AudioThread") {
+#if defined(OS_WIN)
+  thread_.init_com_with_mta(true);
+#endif
+  CHECK(thread_.Start());
+
+#if defined(OS_MACOSX)
+  // On Mac, the audio task runner must belong to the main thread.
+  // See http://crbug.com/158170.
+  task_runner_ = base::ThreadTaskRunnerHandle::Get();
+#else
+  task_runner_ = thread_.task_runner();
+#endif
+  worker_task_runner_ = thread_.task_runner();
+}
+
+AudioThreadImpl::~AudioThreadImpl() {}
+
+void AudioThreadImpl::Stop() {
+  thread_.Stop();
+  task_runner_ = nullptr;

[o1ka, 2017/04/28 13:24:20]

This does not guarantee that task_runner is deleted, right - since it's
ref-counted, and some clients keep a ref ptr to it.

[o1ka, 2017/04/28 13:24:20]

Could you add explanations of how Stop() works in Mac case? Should we DCHECK
that on Mac Stop() is called on task_runner_?

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

Yes I will add more comments and also add a thread-checker.

[alokp, 2017/04/28 17:31:13]

Clients keeping a ref-ptr is OK (although they do not need to and probably
should not). All tasks posted to task runner after the thread has stopped is
immediately discarded.

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

Acknowledged.

[o1ka, 2017/05/02 16:16:01]

sgtm

+  worker_task_runner_ = nullptr;
+}
+
+base::SingleThreadTaskRunner* AudioThreadImpl::GetTaskRunner() {
+  return task_runner_.get();
+}
+
+base::SingleThreadTaskRunner* AudioThreadImpl::GetWorkerTaskRunner() {
+  return worker_task_runner_.get();
+}
+
+}  // namespace media