PaymentHandler: Fix a typo (camelCase to hacker_case).

components/payments/mojom/payment_app.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.
 
 module payments.mojom;
 
 import "components/payments/mojom/payment_request.mojom";
 import "mojo/common/time.mojom";
 import "url/mojo/url.mojom";
 
@@ skipping 42 matching lines @@
   SetPaymentInstrument(string instrument_key, PaymentInstrument instrument)
       => (PaymentHandlerStatus status);
   HasPaymentInstrument(string instrument_key)
       => (PaymentHandlerStatus status);
   GetPaymentInstrument(string instrument_key)
       => (PaymentInstrument instrument, PaymentHandlerStatus status);
 };
 
 struct PaymentAppRequest {
   url.mojom.Url origin;
-  array<PaymentMethodData> methodData;
+  array<PaymentMethodData> method_data;
   PaymentItem total;
   array<PaymentDetailsModifier> modifiers;
-  string optionId;
+  string option_id;
 };
 
 struct PaymentAppResponse {
   string method_name;
   string stringified_details;
 };
 
 // This interface is provided to pass a payment app response from payment
 // request event in renderer side to browser side by calling respondWith().
 interface PaymentAppResponseCallback {
   OnPaymentAppResponse(PaymentAppResponse response,
                        mojo.common.mojom.Time dispatch_event_time);
 };