src/cobalt/black_box_tests/testdata/preload_visibility.html

<!DOCTYPE html>

<head>
  <title>Cobalt preload state visibility test</title>
  <script src='black_box_js_test_utils.js'></script>
</head>

<body>
  <h1>
    <span>ID element</span>
  </h1>
  <script>
    // In preload mode, visibility should be "prerender" and window/document
    // should not have focus.
    assertEqual("prerender", document.visibilityState);
    assertFalse(document.hasFocus());

    // Wait for visibility change to verify visibilityState and having focus.
    function handleVisibilityChange() {
      assertEqual("visible", document.visibilityState);
      assertTrue(document.hasFocus());
      onEndTest();
    }
    document.addEventListener("visibilitychange", handleVisibilityChange);
    setupFinished();
  </script>
</body>