PaymentRequest.abort() should return a promise.

chrome/test/data/android/payments/abort.js

+/*
+ * 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.
+ */
+
+/* global PaymentRequest:false */
+
+var request;
+
+/**
+ * Launches the PaymentRequest UI.
+ */
+function buy() {  // eslint-disable-line no-unused-vars
+  try {
+    request = new PaymentRequest(
+        ['visa'],
+        {total: {label: 'Total', amount: {currency: 'USD', value: '5.00'}}});
+    request.show();
+  } catch (error) {
+    print(error.message);
+  }
+}
+
+/**
+ * Aborts they PaymentRequest.
+ */
+function abort() {  // eslint-disable-line no-unused-vars
+  try {
+    request.abort().then(() => {
+      print('Aborted');
+    }).catch(() => {
+      print('Cannot abort');
+    });
+  } catch (error) {
+    print(error.message);
+  }
+}