ng options.
      // But for the purposes of this demo, we will skip that and proceed immediately.    
      onServerCheckoutDetailsRetrieved(buildShoppingCartDetails());
    }

    function onServerCheckoutDetailsRetrieved(checkoutObject) {
      // The server has constructed the `Checkout` object. Now we know all of the prices 
      // and shipping options.

      if (shouldCallPaymentRequest) {

        var request = new PaymentRequest(buildSupportedPaymentMethodData(),
          checkoutObject);

     