Event.eventType(String type, String name, {bool canBubble: true, bool cancelable: true})

Creates a new Event object of the specified type.

This is analogous to document.createEvent. Normally events should be created via their constructors, if available.

var e = new Event.type('MouseEvent', 'mousedown', true, true);

Source 

factory Event.eventType(String type, String name, {bool canBubble: true,
    bool cancelable: true}) {
  final Event e = document._createEvent(type);
  e._initEvent(name, canBubble, cancelable);
  return e;
}