addPopStateListener method
Adds a listener to the popstate event and returns a function that, when
invoked, removes the listener.
Implementation
ui.VoidCallback addPopStateListener(PopStateListener fn) {
  // No-op.
  return () {};
}Adds a listener to the popstate event and returns a function that, when
invoked, removes the listener.
ui.VoidCallback addPopStateListener(PopStateListener fn) {
  // No-op.
  return () {};
}