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chromium/third_party/blink/web_tests/fast/events/wheel/mouse-wheel-main-frame-scroll.html 

<!DOCTYPE HTML>
<html style="height:100%; overflow:scroll;">
<head>
<script src="../../../resources/testharness.js"></script>
<script src="../../../resources/testharnessreport.js"></script>
<script src="../../../resources/gesture-util.js"></script>
<script src="../../../resources/percent-based-util.js"></script>
</head>
<script>
promise_test(async () => {
  await mouseMoveTo(50, 50);
  const pixelsToScrollY = 100;
  await gestureScroll(() => {
    return smoothScroll(
      pixelsToScrollY, 50, 50, GestureSourceType.MOUSE_INPUT,
      'down', SPEED_INSTANT, !isPercentBasedScrollingEnabled()
    );
  }, document.scrollingElement);
  const { y: expectedScrollY } = calculateExpectedScroll(
    document.scrollingElement, 0, pixelsToScrollY
  );
  assert_approx_equals(window.scrollY, expectedScrollY, 0.001);
}, "Mouse wheel scrolls properly on main frame.");
</script>
<body>
<div style="height:1000px;">
</div>
</body>
</html>