WindowBase opener

A reference to the window that opened this one.

Window thisWindow = window;
WindowBase otherWindow = thisWindow.open('http://www.example.com/', 'foo');
print(otherWindow.opener == thisWindow); // 'true'

Source 

@DomName('Window.opener')
@DocsEditable()
WindowBase get opener => _convertNativeToDart_Window(
    _blink.BlinkWindow.instance.opener_Getter_(this));
void opener=(Window value)

Source 

@DomName('Window.opener')
@DocsEditable()
set opener(Window value) =>
    _blink.BlinkWindow.instance.opener_Setter_(this, value);