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chromium/third_party/blink/perf_tests/paint/multicol-many-columns.html 

<!DOCTYPE html>
<script src="../resources/runner.js"></script>
<script src="resources/paint.js"></script>
<div id="container" style="columns:10000; column-gap:0; column-fill:auto; height:100px;">
  <div style="height:1000000px;"></div>
</div>
<script>
  // Measure paint / pre-paint performance of a multicol container with many
  // columns.

  var wide = false;

measurePaint({
  run: function() {
    container.style.width = wide ? "600px" : "700px";
    wide = !wide;
  },
});
</script>