Enable -Winconsistent-missing-override flag.

webrtc/api/mediastream.h

Index: webrtc/api/mediastream.h
diff --git a/webrtc/api/mediastream.h b/webrtc/api/mediastream.h
index 2a77f0ddc4be6f0b71083e07b18133b0ded2479e..1f80f25207a837668c648987284e2623e83b2eb8 100644
--- a/webrtc/api/mediastream.h
+++ b/webrtc/api/mediastream.h
@@ -31,10 +31,10 @@ class MediaStream : public Notifier<MediaStreamInterface> {
   bool AddTrack(VideoTrackInterface* track) override;
   bool RemoveTrack(AudioTrackInterface* track) override;
   bool RemoveTrack(VideoTrackInterface* track) override;
-  virtual rtc::scoped_refptr<AudioTrackInterface>
-      FindAudioTrack(const std::string& track_id);
-  virtual rtc::scoped_refptr<VideoTrackInterface>
-      FindVideoTrack(const std::string& track_id);
+  rtc::scoped_refptr<AudioTrackInterface>
+      FindAudioTrack(const std::string& track_id) override;
+  rtc::scoped_refptr<VideoTrackInterface>
+      FindVideoTrack(const std::string& track_id) override;
 
   AudioTrackVector GetAudioTracks() override { return audio_tracks_; }
   VideoTrackVector GetVideoTracks() override { return video_tracks_; }