Creates a new MouseEvent.
Source
MouseEvent(
String type, bool bubbles,
num localX, num localY, num stageX, num stageY,
bool altKey, bool ctrlKey, bool shiftKey,
this.deltaX, this.deltaY, this.buttonDown, this.clickCount) : super(
type, bubbles, localX, localY, stageX, stageY,
altKey, ctrlKey, shiftKey);