Pass task runners to AudioManager constructor.

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 3c39e531a9aea3f03cfb018a0ee5430a5b2bf243..bfb74ea6e05537114c4561537f0adb56973d4647 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -73,7 +73,6 @@
 #include "content/public/common/result_codes.h"
 #include "device/battery/battery_status_service.h"
 #include "ipc/mojo/scoped_ipc_support.h"
-#include "media/audio/audio_manager.h"
 #include "media/base/media.h"
 #include "media/base/user_input_monitor.h"
 #include "media/midi/midi_manager.h"
@@ -1223,8 +1222,32 @@ int BrowserMainLoop::BrowserThreadsStarted() {
 
   {
     TRACE_EVENT0("startup", "BrowserThreadsStarted::Subsystem:AudioMan");
-    audio_manager_.reset(media::AudioManager::CreateWithHangTimer(
-        MediaInternals::GetInstance(), io_thread_->task_runner()));
+    // TODO(alokp): Allow content embedders to override the default
+    // task runners by defining ContentBrowserClient::GetAudioTaskRunner.
+    scoped_refptr<base::SingleThreadTaskRunner> audio_task_runner;
+    scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner;
+    scoped_refptr<base::SingleThreadTaskRunner> monitor_task_runner;
+    audio_thread_.reset(new base::Thread("AudioThread"));
+#if defined(OS_WIN)
+    audio_thread_->init_com_with_mta(true);
+#endif  // defined(OS_WIN)
+    CHECK(audio_thread_->Start());

[DaleCurtis, 2016/03/22 21:58:27]

It's unfortunate that we'll always start this now, previously OSX didn't unless
the worker task runner was used. It's probably a minor thing though if it's
never used.

[alokp, 2016/03/22 22:23:39]

Yeah I could not think of a way to avoid this.

+    media::AudioLogFactory* audio_log_factory = MediaInternals::GetInstance();

[DaleCurtis, 2016/03/22 21:58:27]

Seems unnecessary to break this out. I'd just inline.

[alokp, 2016/03/22 22:23:39]

Done.

+#if defined(OS_MACOSX)
+    // On Mac audio task runner must belong to the main thread.
+    // See http://crbug.com/158170.
+    // Since the audio thread is the UI thread, a hang monitor is not
+    // necessary or recommended.
+    audio_task_runner = base::ThreadTaskRunnerHandle::Get();
+    worker_task_runner = audio_thread_->task_runner();
+#else
+    audio_task_runner = audio_thread_->task_runner();
+    worker_task_runner = audio_thread_->task_runner();
+    monitor_task_runner = io_thread_->task_runner();
+#endif  // defined(OS_MACOSX)
+    audio_manager_ = media::AudioManager::Create(
+        std::move(audio_task_runner), std::move(worker_task_runner),
+        std::move(monitor_task_runner), audio_log_factory);
   }
 
   {