Add layout tests for the audio component of MediaStream Recording.

content/public/renderer/media_stream_api.h

Index: content/public/renderer/media_stream_api.h
diff --git a/content/public/renderer/media_stream_api.h b/content/public/renderer/media_stream_api.h
index 2e87ff3cd1491adf2979dcd1c19f11c1b26fd8b1..dfb2aaf6ea1161d61c513b8634dedc460f98df54 100644
--- a/content/public/renderer/media_stream_api.h
+++ b/content/public/renderer/media_stream_api.h
@@ -43,6 +43,11 @@ CONTENT_EXPORT bool AddAudioTrackToMediaStream(
     bool is_remote,
     bool is_readonly,
     const std::string& media_stream_url);
+CONTENT_EXPORT bool AddAudioTrackToMediaStream(
+    const scoped_refptr<media::AudioCapturerSource>& source,
+    bool is_remote,
+    bool is_readonly,
+    blink::WebMediaStream* web_stream);
 
 }  // namespace content