Browser.addVisibilityWindowListener(
VisibilityWindowListener listener)
Adds the listener to the collection of listeners who will be
notified when a window hosting the receiver needs to be displayed
or hidden.
void
Browser.removeVisibilityWindowListener(
VisibilityWindowListener listener)
Removes the listener from the collection of listeners who will
be notified when a window hosting the receiver needs to be displayed
or hidden.