anchor.diff:  }
   
   @JS()
  -@anonymous
   class SyntheticAnimationEvent extends SyntheticEvent {
     external String get animationName;
     external num get elapsedTime;
  
positive.code: }
  
  @JS()
  @anonymous
  class SyntheticTransitionEvent extends SyntheticEvent {
    external String get propertyName;
    external num get elapsedTime;
  
negative.code: }
  
  @JS()
  class SyntheticUIEvent extends SyntheticEvent {
    external num get detail;
    external get view;
  }
  
  @JS()
  class SyntheticWheelEvent extends SyntheticEvent {
    external num get deltaX;
    external num get deltaMode;
  