Add browser test for getusermedia and unavailable audio device.

media/audio/audio_manager_base.cc

Index: media/audio/audio_manager_base.cc
diff --git a/media/audio/audio_manager_base.cc b/media/audio/audio_manager_base.cc
index dd6e9a2a3098a57517a3553596149e877dfc1963..670820dc3a6ad0f446d429cd97b4e3a7484f5c67 100644
--- a/media/audio/audio_manager_base.cc
+++ b/media/audio/audio_manager_base.cc
@@ -433,4 +433,10 @@ std::unique_ptr<AudioLog> AudioManagerBase::CreateAudioLog(
   return audio_log_factory_->CreateAudioLog(component);
 }
 
+void AudioManagerBase::SetMaxStreamCountForTesting(int max_input,
+                                                   int max_output) {
+  max_num_output_streams_ = max_output;
+  max_num_input_streams_ = max_input;
+}
+
 }  // namespace media