Ensure both default audio device IDs are handled for creation.

media/audio/audio_output_proxy.h

Index: media/audio/audio_output_proxy.h
diff --git a/media/audio/audio_output_proxy.h b/media/audio/audio_output_proxy.h
index 504b4efbe44a1e151ff683bca9862b155638875b..d4fd56ca31855bf2936f4b55a939675cf7a06677 100644
--- a/media/audio/audio_output_proxy.h
+++ b/media/audio/audio_output_proxy.h
@@ -39,6 +39,10 @@ class MEDIA_EXPORT AudioOutputProxy
   void GetVolume(double* volume) override;
   void Close() override;
 
+  AudioOutputDispatcher* get_dispatcher_for_testing() const {
+    return dispatcher_.get();
+  }
+
  private:
   enum State {
     kCreated,