Add data parameter to payment details modifier.

components/payments/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 blink.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 79 matching lines @@
   string id;
   string label;
   PaymentCurrencyAmount amount;
   bool selected;
 };
 
 struct PaymentDetailsModifier {
   array<string> supported_methods;
   PaymentItem? total;
   array<PaymentItem> additional_display_items;
+  // A JSON string built by the renderer from a JavaScript object that the

[Tom Sepez, 2016/11/02 20:23:22]

Parsing such an object in the browser is generally frowned upon; we use JSON in
the browser, but only when coming from a trusted source.

Do we need to process this in the browser or just pass it thru?  Presumably the
payment app can defend itself from malformed input?

[please use gerrit instead, 2016/11/02 20:35:17]

PaymentRequestImpl.java sanitizes and parses the string to JSONObject to
validate that the renderer is giving a valid JSON string to the browser. If
that's not the case, the browser tears down the Mojo pipe and closes the
payments UI.

AndroidPayPaymentApp.java and AndroidPayPaymentInstrument.java (not public)
process the JSONObject to determine the flags to use when calling into Android
Pay.

Once 3rd party payment apps are implemented, they will start receiving this as a
string. They will be responsible for protecting themselves.

+  // merchant website provides. The renderer uses
+  // blink::JSONObject::toJSONString() to generate this string. The browser
+  // parses the string via JSONObject(JsonSanitizer.sanitize(stringified_data))
+  // and passes a part of the JSON object to the payment app, for example
+  // Android Pay. There's no one format for this object, so richer types cannot
+  // be used. A simple example:
+  //
+  // {"gateway": "stripe"}
+  string stringified_data;
 };
 
 struct PaymentDetails {
   PaymentItem total;
   array<PaymentItem> display_items;
   array<PaymentShippingOption> shipping_options;
   array<PaymentDetailsModifier> modifiers;
   string error;
 };
 
@@ skipping 34 matching lines @@
 interface PaymentRequest {
   Init(PaymentRequestClient client,
        array<PaymentMethodData> methodData,
        PaymentDetails details,
        PaymentOptions options);
   Show();
   UpdateWith(PaymentDetails details);
   Abort();
   Complete(PaymentComplete result);
 };