fune/testing/web-platform/tests/navigation-timing/test_readwrite.html

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8" />
        <title>window.performance is read/write</title>
        <link rel="author" title="Microsoft" href="http://www.microsoft.com/" />
        <link rel="help" href="http://www.w3.org/TR/navigation-timing/#sec-window.performance-attribute"/>
        <meta name="assert" content="The window.performance attribute provides a hosting area for performance related attributes. "/>
        <script src="/resources/testharness.js"></script>
        <script src="/resources/testharnessreport.js"></script>
        <script src="/common/performance-timeline-utils.js"></script>
        <script src="resources/webperftestharness.js"></script>
    </head>
    <body>
        <h1>Description</h1>
        <p>This test validates that the window.performance object is read/write.</p>
        <div id="log"></div>
        <script>
            test_namespace();

            window.performance = 'foo';
            test_equals(window.performance, 'foo', 'window.performance is read/write');

            var performance = 'bar';
            test_equals(performance, 'bar', 'var performance is read/write');
        </script>
    </body>
</html>