virtual nsresult DragGesture(nsIDOMEvent* aDragEvent) { return NS_OK; }
virtual nsresult DragGesture(nsIDOMEvent* aEvent) { return mFrame ? mFrame->DragGesture(aEvent) : NS_OK; }
  virtual nsresult DragGesture(nsIDOMEvent* aDragEvent) { return NS_OK; } 