Add browser test for getusermedia and unavailable audio device.

media/audio/audio_manager_base.h

Index: media/audio/audio_manager_base.h
diff --git a/media/audio/audio_manager_base.h b/media/audio/audio_manager_base.h
index 4dc3fd3fd727f3a820e9c07ae5c03213f1f188da..b3100cf6c507bb6cb6af2086806356cc3c6de15a 100644
--- a/media/audio/audio_manager_base.h
+++ b/media/audio/audio_manager_base.h
@@ -68,6 +68,8 @@ class MEDIA_EXPORT AudioManagerBase : public AudioManager {
   std::unique_ptr<AudioLog> CreateAudioLog(
       AudioLogFactory::AudioComponent component) override;
 
+  void SetMaxStreamCountForTesting(int max_input, int max_output) final;
+
   // AudioManagerBase:
 
   // Called internally by the audio stream when it has been closed.