Pretend the video has no audio track if it is playing as part of autoplay muted.

media/blink/webmediaplayer_impl.h

Index: media/blink/webmediaplayer_impl.h
diff --git a/media/blink/webmediaplayer_impl.h b/media/blink/webmediaplayer_impl.h
index 8fcae51c904b86ce45a47e463d2ef69341a3ce10..b6a359cdfd3dfcfbc44d029edbb136f48679d2a8 100644
--- a/media/blink/webmediaplayer_impl.h
+++ b/media/blink/webmediaplayer_impl.h
@@ -554,6 +554,9 @@ class MEDIA_BLINK_EXPORT WebMediaPlayerImpl
   int underflow_count_;
   std::unique_ptr<base::ElapsedTimer> underflow_timer_;
 
+  // Whether the player is currently in autoplay muted state.
+  bool autoplay_muted_ = false;
+
   DISALLOW_COPY_AND_ASSIGN(WebMediaPlayerImpl);
 };