Audio indicator: cross platform drawing and animation

chrome/browser/media/audio_stream_indicator.h

Index: chrome/browser/media/audio_stream_indicator.h
diff --git a/chrome/browser/media/audio_stream_indicator.h b/chrome/browser/media/audio_stream_indicator.h
index 8c4f5357d6e689d86243bc2de9f18f8627adb4b1..da6639934b820a18dc34765dea62b4a7ea8b7d38 100644
--- a/chrome/browser/media/audio_stream_indicator.h
+++ b/chrome/browser/media/audio_stream_indicator.h
@@ -13,6 +13,7 @@
 namespace content {
 class WebContents;
 }
+class TabAudioIndicatorTest;
 
 class AudioStreamIndicator
     : public base::RefCountedThreadSafe<AudioStreamIndicator> {
@@ -25,10 +26,12 @@ class AudioStreamIndicator
                                int stream_id,
                                bool is_playing_and_audible);
 
-  // This method should be called on the IO thread.
+  // This method should be called on the UI thread.
   bool IsPlayingAudio(content::WebContents* contents);
 
  private:
+  friend class TabAudioIndicatorTest;
+
   struct RenderViewId {
     RenderViewId(int render_process_id,
                  int render_view_id);