Intiialize AudioManager and related class lazily

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 b53236dd828b8a7eaeffe2e4de7ee55406f8a46b..2a2f8b92514e7d0a4330f4a6b9ec40272f729ee9 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -1470,7 +1470,6 @@ void BrowserMainLoop::CreateAudioManager() {
   DCHECK(!audio_thread_);
   DCHECK(!audio_manager_);
 
-  bool use_hang_monitor = true;
   audio_manager_ = GetContentClient()->browser()->CreateAudioManager(
       MediaInternals::GetInstance());
   if (!audio_manager_) {
@@ -1482,9 +1481,6 @@ void BrowserMainLoop::CreateAudioManager() {
 #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.
-    use_hang_monitor = false;
     scoped_refptr<base::SingleThreadTaskRunner> audio_task_runner =
         base::ThreadTaskRunnerHandle::Get();
 #else
@@ -1498,9 +1494,6 @@ void BrowserMainLoop::CreateAudioManager() {
                                                  MediaInternals::GetInstance());
   }
   CHECK(audio_manager_);
-
-  if (use_hang_monitor)
-    media::AudioManager::StartHangMonitor(io_thread_->task_runner());
 }
 
 }  // namespace content