anchor.diff:  class SoundEffectStream {
     SoundEffectStream(
       this.sound,
  -    this.tag,
       this.loop,
       this.volume,
       this.pitch,
  
positive.code:     // Create new PlayingSound object
      SoundEffectStream playingSound = new SoundEffectStream(
        sound,
        tag,
        loop,
        volume,
        pitch,
  
negative.code:   double volume = 1.0;
    double pitch = 1.0;
    double pan = 0.0;
  
    // TODO: Implement completion callback. On completion, sounds should
    // also be removed from the list of playing sounds.
  