chromium/src/third_party/blink/web_tests/fast/spatial-navigation/snav-stay-in-overflow-div.html

<style>
  div#scroller {
    /* The div displays one line of text at once. */
    line-height: 1.5em;
    height: 1.5em;
    overflow-y: scroll;
  }
</style>

<div id="scroller">
  <a href="#" id="a">a</a><br>
  <a href="#" id="b">b</a>
</div>
<a href="#" id="c">c</a>

<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<script src="resources/snav-testharness.js"></script>
<script>
var resultMap = [
  ["Down", "a"], // Scrolled so no focus change.
  ["Down", "b"],
  ["Down", "c"],
  ["Up", "scroller"],
  ["Up", "b"],
  ["Up", "b"],   // Scrolled so no focus change.
  ["Up", "a"],
];
  // Start at a known place.
  document.getElementById("a").focus();
  snav.assertFocusMoves(resultMap);
</script>