Show at most one PaymentRequest UI at a time.

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

Index: chrome/test/data/android/payments/show_twice.js
diff --git a/chrome/test/data/android/payments/show_twice.js b/chrome/test/data/android/payments/show_twice.js
new file mode 100644
index 0000000000000000000000000000000000000000..e870f4e57a2fbb0a844cd78770c4cb365600de86
--- /dev/null
+++ b/chrome/test/data/android/payments/show_twice.js
@@ -0,0 +1,23 @@
+/*
+ * 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 */
+
+/**
+ * Launches the PaymentRequest UI twice.
+ */
+function buy() {  // eslint-disable-line no-unused-vars
+  var payment1 = new PaymentRequest(
+      [{supportedMethods: ['visa']}],
+      {total: {label: 'Total', amount: {currency: 'USD', value: '5.00'}}});
+  var payment2 = new PaymentRequest(
+      [{supportedMethods: ['visa']}],
+      {total: {label: 'Total', amount: {currency: 'USD', value: '5.00'}}});
+  payment1.show();
+  payment2.show().catch(function(error) {
+    print("Second request: " + error);
+  });
+}