Accept any string for currency code in PaymentRequest.

third_party/WebKit/public/platform/modules/payments/payment_request.mojom

Index: third_party/WebKit/public/platform/modules/payments/payment_request.mojom
diff --git a/third_party/WebKit/public/platform/modules/payments/payment_request.mojom b/third_party/WebKit/public/platform/modules/payments/payment_request.mojom
index dc29676287b9305099250111afb74bb15a1538b9..161240fe9c55ad8b25bb6a9dea4e6a7d6201c14c 100644
--- a/third_party/WebKit/public/platform/modules/payments/payment_request.mojom
+++ b/third_party/WebKit/public/platform/modules/payments/payment_request.mojom
@@ -36,7 +36,9 @@ struct PaymentAddress {
 // 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