LabelDragRenderer draws a label at the current mouse location. Typically this one overrides this class and calls the setLabel and super.renderDrag classes.
create an instance.
create an instance, and presumably the mouse module will set the parent.
This method is called by the DMIA on mouse release. We use this to infer the mouse release and hide the Window. Note this assumes isUpdatingDragSelection is false! TODO: DMIA should call clear so this is more explicit.
set the label to be drawn. This should be done before this object's renderDrag is called.