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chromium/third_party/blink/web_tests/compositing/squashing/frame-clip-squashed-scrolled.html 

<!DOCTYPE html>
<script src="../../paint/invalidation/resources/text-based-repaint.js"></script>
<div style="will-change: transform"></div>
<div style="position: relative; width: 100px; border: 1px solid black">
  <div style="width: 50px; height: 2000px; background: green"></div>
</div>
There should be a green rectangle across the entire height of the screen
<script>
  function repaintTest() {
    window.scrollBy(0, 300);
  }
  onload = runRepaintAndPixelTest;
</script>