anchor.diff:  }
   
   @JS()
  -@anonymous
   class SyntheticAnimationEvent extends SyntheticEvent {
     external String get animationName;
     external num get elapsedTime;
  
positive.code: }
  
  @JS()
  @anonymous
  class SyntheticCompositionEvent extends SyntheticEvent {
    external String get data;
  }
  
  @JS()
  @anonymous
  class SyntheticFocusEvent extends SyntheticEvent {
    external EventTarget get relatedTarget;
  }
  
  @JS()
  @anonymous
  class SyntheticFormEvent extends SyntheticEvent {}
  
  /// A JS object that looks like a [DataTransfer] but isn't one.
  ///
  /// See `syntheticDataTransferFactory` for more info.
  @JS()
  @anonymous
  class NonNativeDataTransfer {
    external String get dropEffect;
    external String get effectAllowed;
  
negative.code: }
  
  @JS()
  class SyntheticPointerEvent extends SyntheticEvent {
    external num get pointerId;
    external num get width;
  