Monitor the IO message loop in the AudioDevice classes.

media/audio/audio_manager_base.cc

 // Copyright (c) 2012 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_manager_base.h"
 
 #include "base/bind.h"
 #include "base/message_loop_proxy.h"
 #include "base/threading/thread.h"
 #include "media/audio/audio_output_dispatcher.h"
@@ skipping 89 matching lines @@
 void AudioManagerBase::Shutdown() {
   // To avoid running into deadlocks while we stop the thread, shut it down
   // via a local variable while not holding the audio thread lock.
   scoped_ptr<base::Thread> audio_thread;
   {
     base::AutoLock lock(audio_thread_lock_);
     audio_thread_.swap(audio_thread);
   }
 
   if (!audio_thread.get())
-      return;
+    return;
 
   CHECK_NE(MessageLoop::current(), audio_thread->message_loop());
 
   // We must use base::Unretained since Shutdown might have been called from
   // the destructor and we can't alter the refcount of the object at that point.
   audio_thread->message_loop()->PostTask(FROM_HERE, base::Bind(
       &AudioManagerBase::ShutdownOnAudioThread,
       base::Unretained(this)));
 
   // Stop() will wait for any posted messages to be processed first.
@@ skipping 15 matching lines @@
       // both physical audio stream objects that belong to the dispatcher as
       // well as the message loop of the audio thread that will soon go away.
       // So, better crash now than later.
       CHECK(dispatcher->HasOneRef()) << "AudioOutputProxies are still alive";
       dispatcher = NULL;
     }
   }
 
   output_dispatchers_.clear();
 }