title: NW.js - Hiding window should bring last Application to focus
body: <p>long story short: I'm opening a window which should not quit the whole application when closing the window. That works just fine. But closing it won't return focus to the last window of the last application (like Chrome or Terminal)</p>
  
  <pre><code>win = nw.Window.open(
    'view.html',
    {
      width: 300,
      height: 400,
      show: false, // I show the window when DOM has been loaded.
    },
    function( win ) {
      win.setShowInTaskbar( false );
  
      win.on( 'close', function() {
        this.hide();
      } );
    }
  );
  </code></pre>
  
  <p>Does anyone know how to give the last window it's focus back?
  Thanks for any help!</p>