Accept any string for currency code in PaymentRequest.

third_party/WebKit/public/platform/modules/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.mojom.payments"]
 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 18 matching lines @@
   string organization;
   string recipient;
   string careOf;
   string phone;
 };
 
 // The currency amount that the renderer provides to the browser process. The
 // browser shows the amount in UI and forwards it on to the payment app, if it
 // requires the amount.
 struct PaymentCurrencyAmount {
-  // ISO 4217 currency code. Three upper case ASCII letters.
+  // The most common identifiers are three-letter alphabetic codes as defined
+  // by [ISO4217] (for example, "USD" for US Dollars), however any string of at
+  // most 2048 characters is considered valid.
   string currency;
 
   // ISO 20022 CurrencyAnd30Amount. Up to 30 total digits. Up to 10 fraction
   // digits. Separated by a dot.
   string value;
 };
 
 struct PaymentResponse {
   string method_name;
 
@@ skipping 82 matching lines @@
 interface PaymentRequest {
   Init(PaymentRequestClient client,
        array<PaymentMethodData> methodData,
        PaymentDetails details,
        PaymentOptions options);
   Show();
   UpdateWith(PaymentDetails details);
   Abort();
   Complete(PaymentComplete result);
 };