fullscreen/rendering/fullscreen-root-block-scroll.html

<!DOCTYPE html>
<style>
  body {
    height: 10000px;
    background: grey;
  }
</style>
<title>fullscreen root block scrolling</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-vendor.js"></script>
<script src="../trusted-click.js"></script>
<body>
<div>
  This page tests that entering fullscreen doesn't adjust the scroll offset
</div>
<script>
  promise_test(async (t) => {
    t.add_cleanup(() => {
      if (document.fullscreenElement) {
        return document.exitFullscreen();
      }
    });
    await trusted_click();
    document.scrollingElement.scrollTop = 300;
    await document.documentElement.requestFullscreen();
    await fullScreenChange();

    assert_equals(document.fullscreenElement, document.documentElement);
    assert_not_equals(document.scrollingElement.scrollTop, 0);
    document.scrollingElement.scrollTop = 0;
  });
</script>