echo_message.html | Explore in Territory

<!-- Copyright 2022 The Chromium Authors
     Use of this source code is governed by a BSD-style license that can be
     found in the LICENSE file. -->

<!doctype html>
<html>
  Sandboxed Page
  <script>
    onmessage = (e) => {
      e.source.postMessage('echo ' + e.data, '*');
    };
  </script>
</html>

chromium/chrome/test/data/extensions/echo_message.html