PaymentApp: Remove unncessary comments in PaymentRequestEvent.idl.

third_party/WebKit/Source/modules/payments/PaymentRequestEvent.idl

 // 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.
 
 // https://w3c.github.io/webpayments-payment-apps-api/#idl-def-paymentrequestevent
 
 [
     RuntimeEnabled=PaymentApp,
     Exposed=ServiceWorker
 ] interface PaymentRequestEvent : ExtendableEvent {
     readonly attribute PaymentAppRequestData data;
-    // The payment app api spec says that respondWith() should take a union
-    // type as follows:
-    //  - respondWith((Promise<PaymentResponse> or PaymentResponse));
-    //
-    // But the web-idl spec says that Promise types are not distinguishable
-    // with any other type. Also, if we pass PaymentResponse to respondWith(),
-    // then it will just be cast to a promise immediately via Promise.resolve().
-    //
-    // We found existing case here:
-    //  - https://github.com/w3c/ServiceWorker/issues/724
-    //
-    // So, we should just use Promise<PaymentResponse> instead of union type.
-    // Related spec bug:
-    //  - https://github.com/w3c/webpayments-payment-apps-api/pull/71
     void respondWith(Promise<PaymentResponse> response);
 };