chromium/third_party/blink/web_tests/external/wpt/css/css-overflow/scroll-with-border-radius.html

<!doctype html>
<meta charset=utf-8>
<title>Should not scroll out of rounded corner</title>
<link rel="help" href="https://crbug.com/40277896">
<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="/resources/testdriver-actions.js"></script>
<script src="/dom/events/scrolling/scroll_support.js"></script>
<style>
  #scroller {
    border-radius: 100px;
    overflow: auto;
    width: 300px;
    height: 300px;
    border: 2px solid blue;
    will-change: scroll-position;
  }

  .spacer {
    height: 200vh;
  }

</style>

<div id="scroller">
  <div class="spacer"></div>
</div>
<div class="spacer"></div>

<script>
  promise_test(async (t) => {
    await waitForCompositorCommit();
    let scrolled = new Promise((resolve) => {
      let scrollers = [window, document.getElementById("scroller")];
      let onscroll = (evt) => {
        for (const scroller of scrollers) {
          scroller.removeEventListener("scroll", onscroll);
        }
        resolve(evt.target.id || "root");
      }
      for (const scroller of scrollers) {
        scroller.addEventListener("scroll", onscroll);
      }
    });
    const actions = new test_driver.Actions().scroll(20, 20, 0, 50, { duration: 50 });
    actions.send();
    assert_equals(await scrolled, "root", "Incorrect element scrolled");
  }, "Wheel-scroll out of rounded corner skips that scroller");
</script>