[Payments] Implement openWindow for service worker based payment handler

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/payment-handler/#the-paymentrequestevent
 
 // TODO(zino): Once the spec issue is resolved, we should apply the changes.
 // Please see https://github.com/w3c/payment-handler/pull/162
 [
     RuntimeEnabled=PaymentApp,
     Exposed=ServiceWorker
 ] interface PaymentRequestEvent : ExtendableEvent {
     readonly attribute DOMString topLevelOrigin;
     readonly attribute DOMString paymentRequestOrigin;
     readonly attribute DOMString paymentRequestId;
     readonly attribute sequence<PaymentMethodData> methodData;
     readonly attribute PaymentItem total;
     readonly attribute sequence<PaymentDetailsModifier> modifiers;
     readonly attribute DOMString instrumentKey;
 
-    // TODO(gogerald): We should implement this function.
-    // Please see: http://crbug.com/720027
-    // Promise<WindowClient> openWindow(USVString url);
+    [CallWith=ScriptState] Promise<WindowClient?> openWindow(USVString url);

[zino, 2017/05/25 17:02:42]

This should be Promise<WindowClient> according to the spec.
Please see my another comment:
https://codereview.chromium.org/2893823004/patch/140001/150020

[please use gerrit instead, 2017/05/25 17:56:13]

What zino said.

[gogerald1, 2017/05/29 22:13:16]

Done.

     [CallWith=ScriptState, RaisesException] void respondWith(Promise<PaymentResponse> response);
 };