agregando funcionalidad para detectar la cancelación del pago

Author: JavierAnaya

src/paypal-checkout.android.ts

@@ -29,6 +29,13 @@ export class PaypalCheckout extends Common {
                 })
             );
 
+            braintree.addListener(new com.braintreepayments.api.interfaces.BraintreeCancelListener({
+                    onCancel: function (requestCode) {
+                        reject("Buyer canceled payment approval");
+                    }
+                })
+            );
+
             braintree.addListener(new com.braintreepayments.api.interfaces.BraintreeErrorListener({
                     onError: function(error) {
                         reject(error);

src/paypal-checkout.ios.ts

@@ -19,7 +19,7 @@ export class PaypalCheckout extends Common {
             payPalDriver.requestOneTimePaymentCompletion(request, function(tokenizedPayPalAccount, error) {
                 if (tokenizedPayPalAccount) {
                     resolve(tokenizedPayPalAccount.nonce);
-                }else if (error) {
+                } else if (error) {
                     reject(error);
                 } else {
                     reject("Buyer canceled payment approval");