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..d93e49cc3b85c83bf637483f58bd16fe892aa101 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/scoped_loop_observer.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 ScopedLoopObserver,
       public base::RefCountedThreadSafe<AudioInputDevice> {
  public:
   class CONTENT_EXPORT CaptureCallback {
@@ -176,6 +178,10 @@ class CONTENT_EXPORT AudioInputDevice
   // DelegateSimpleThread::Delegate implementation.
   virtual void Run() OVERRIDE;
 
+  // MessageLoop::DestructionObserver implementation for the IO loop.
+  // If the IO loop dies before we do, we shut down the audio thread from here.
+  virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
+
   // Format
   AudioParameters audio_parameters_;