PaymentRequest: Introduce PaymentDetailsInit and PaymentDetailsUpdate.

components/payments/content/payment_request.mojom

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [JavaPackage="org.chromium.payments.mojom"]
 module payments.mojom;
 
 // The shipping address that the browser process provides to the renderer
 // process. Built either by the browser or a payment app.
 struct PaymentAddress {
@@ skipping 165 matching lines @@
   array<BasicCardType> supported_types;
 };
 
 struct PaymentDetailsModifier {
   PaymentItem? total;
   array<PaymentItem> additional_display_items;
   PaymentMethodData method_data;
 };
 
 struct PaymentDetails {
-  PaymentItem total;
+  PaymentItem? total;
   array<PaymentItem> display_items;
   array<PaymentShippingOption> shipping_options;
   array<PaymentDetailsModifier> modifiers;
-  string error;
+  string error = "";
 };
 
 enum PaymentShippingType {
   SHIPPING,
   DELIVERY,
   PICKUP
 };
 
 struct PaymentOptions {
   bool request_payer_name;
@@ skipping 13 matching lines @@
   Init(PaymentRequestClient client,
        array<PaymentMethodData> method_data,
        PaymentDetails details,
        PaymentOptions options);
   Show();
   UpdateWith(PaymentDetails details);
   Abort();
   Complete(PaymentComplete result);
   CanMakePayment();
 };