horizontal-smooth-scroll-in-rtl.html

<!DOCTYPE HTML>
<script src="../../../../../resources/testharness.js"></script>
<script src="../../../../../resources/testharnessreport.js"></script>
<script src='../../../../../resources/gesture-util.js'></script>
<title>The first programmatic smooth scroll runs on compositor</title>
<style>

html {
  writing-mode: vertical-rl;
  width: 1000px;
}

</style>
<script>
promise_test(async () => {
  await waitForCompositorCommit();
  await keyboardScroll("ArrowLeft", document);
  assert_equals(window.scrollX, -KEYBOARD_SCROLL_PIXELS);

  // Scrolling right to return to the start position.
  await waitForWindowScrollBy({
    left: KEYBOARD_SCROLL_PIXELS, behavior: "smooth" });
  assert_equals(window.scrollX, 0);
}, "This test verifies that both input-driven and programmatic " +
    "smooth scrolls serviced by the compositor thread go to the correct " +
    "scroll position on RTL pages with horizontal overflow.");
</script>

chromium/third_party/blink/web_tests/virtual/threaded-prefer-compositing/fast/scroll-behavior/smooth-scroll/horizontal-smooth-scroll-in-rtl.html