1. @DomName('Navigator.sendBeacon')
  2. @DocsEditable()
  3. @Experimental()
bool sendBeacon(String url, Object data)

Source 

@DomName('Navigator.sendBeacon')
@DocsEditable()
@Experimental() // untriaged
bool sendBeacon(String url, Object data) =>
    _blink.BlinkNavigator.instance.sendBeacon_Callback_2_(this, url, data);