chromium/third_party/blink/web_tests/fast/events/keyboard-scroll-use-count.html

<!DOCTYPE html>
<style>
#scrollable {
    height: 800px;
    width: 800px;
    overflow: auto;
}
#content {
    height: 4000px;
    width: 800px;
}
</style>

<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<div id="scrollable">
    <div id="content"> </div>
</div>

<script>
// values are from enum Feature in UseCounter.h
var ScrollByKeyboardArrowKeys = 1843;
var ScrollByKeyboardPageUpDownKeys = 1844;
var ScrollByKeyboardHomeEndKeys = 1845;
var ScrollByKeyboardSpacebarKey = 1846;

test(function() {
  if (!window.eventSender)
      return;
  
  var rect = document.getElementById("scrollable").getBoundingClientRect();
  var startX = (rect.left + rect.right) / 2;
  var startY = (rect.top + rect.bottom) / 2;

  // Make sure that scrollable will scroll.
  eventSender.mouseMoveTo(startX, startY);
  eventSender.mouseDown();
  eventSender.mouseUp();

  scrollByArrowKey();
  scrollBySpaceKey();
  scrollByPage();
  scrollByEndKey();
    
}, "Tests that scrolling by keyboard keys is recorded in UMA usecounter."); 

function scrollByArrowKey() {
  eventSender.keyDown('ArrowDown');
  assert_true(internals.isUseCounted(document, ScrollByKeyboardArrowKeys));
}

function scrollBySpaceKey() {
  eventSender.keyDown(" ", []);
  assert_true(internals.isUseCounted(document, ScrollByKeyboardSpacebarKey));
}

function scrollByPage() {
  if (navigator.platform.indexOf('Mac') == 0) {
      eventSender.keyDown('ArrowDown', ["altKey"]);
  } else {
      eventSender.keyDown('PageDown');
  }
  assert_true(internals.isUseCounted(document,
                                     ScrollByKeyboardPageUpDownKeys));
}

function scrollByEndKey() {
  eventSender.keyDown('End');
  assert_true(internals.isUseCounted(document, ScrollByKeyboardHomeEndKeys));
}
</script>