Monitor the IO message loop in the AudioDevice classes.

content/renderer/media/audio_input_device.h

Index: content/renderer/media/audio_input_device.h
diff --git a/content/renderer/media/audio_input_device.h b/content/renderer/media/audio_input_device.h
index 96dd2ff3ee779f0820b700312799d9319e86de91..e6e6f6a7c2aa7277ec2f689f104530754aa3ae44 100644
--- a/content/renderer/media/audio_input_device.h
+++ b/content/renderer/media/audio_input_device.h
@@ -78,6 +78,7 @@
 #include "base/threading/simple_thread.h"
 #include "content/common/content_export.h"
 #include "content/renderer/media/audio_input_message_filter.h"
+#include "content/renderer/media/audio_device.h"
 #include "media/audio/audio_parameters.h"
 
 // TODO(henrika): This class is based on the AudioDevice class and it has
@@ -88,6 +89,7 @@
 class CONTENT_EXPORT AudioInputDevice
     : public AudioInputMessageFilter::Delegate,
       public base::DelegateSimpleThread::Delegate,
+      public AudioDeviceIOLoopObserver<AudioInputDevice>,
       public base::RefCountedThreadSafe<AudioInputDevice> {
  public:
   class CONTENT_EXPORT CaptureCallback {
@@ -162,6 +164,8 @@ class CONTENT_EXPORT AudioInputDevice
   void InitializeOnIOThread();
   void SetSessionIdOnIOThread(int session_id);
   void StartOnIOThread();
+  // Allow AudioDeviceIOLoopObserver to call ShutDownOnIOThread.
+  friend class AudioDeviceIOLoopObserver<AudioInputDevice>;
   void ShutDownOnIOThread(base::WaitableEvent* completion);
   void SetVolumeOnIOThread(double volume);
   // Closes socket and joins with the audio thread.