chromium/components/test/data/payments/app_store_billing_tests/index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=0.5, maximum-scale=0.5, minimum-scale=0.5">
  </head>
  <body>
    <button onclick="addSupportedMethod('https://play.google.com/billing')">addSupportedMethod('https://play.google.com/billing')</button>
    <button onclick="createPaymentRequest()">create PaymentRequest</button>
    <button onclick="show()">show</button>
    <pre id="msg"></pre>
  </body>
  <script src="index.js"></script>
  <script src="util.js"></script>
</html>