chromium/third_party/blink/web_tests/http/tests/misc/link-rel-prefetch.html

<html>
<head>
  <script>
    window.addEventListener('load', e => {
        if (window.testRunner) {
            testRunner.dumpAsText();
            testRunner.waitUntilDone();
        }
    }, false);

    var linkLoadCount = 3;
    function decrementLinkLoadCount()
    {
        linkLoadCount--;
        if (linkLoadCount == 0 && window.testRunner)
            window.testRunner.notifyDone();
    }
  </script>
  <link rel=prefetch onload="decrementLinkLoadCount()" href="/resources/square100.png">
  <link rel=prefetch onload="decrementLinkLoadCount()" href="/resources/square200.png">
  <link rel=prefetch onload="decrementLinkLoadCount()" href="/resources/square20.png">
</head>
</html>