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chromium/third_party/blink/web_tests/paint/invalidation/scroll/iframe-scrollbar-hover.html 

<!DOCTYPE html>
<script src="../resources/text-based-repaint.js"></script>
<script>
function repaintTest() {
  eventSender.mouseMoveTo(195, 120);
}
if (window.eventSender)
  onload = runRepaintTest;
</script>
Tests paint invalidation when mouse hovers on the scrollbar in an iframe.
<iframe id="iframe"
    style="position: absolute; top: 100px; left: 0; width: 200px; height: 200px"
    srcdoc="<div style='height: 300px'></div>"></iframe>