<!DOCTYPE HTML>
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<html>
<head>
  <meta charset="utf-8">
  <title>Verify correct sizing of flex tracks when using subgrid in CSS Masonry</title>
  <link rel="author" title="Brandon Stewart" href="mailto:brandonstewart@apple.com">
  <link rel="help" href="https://drafts.csswg.org/css-grid-3/#subgrids">
  <style>
    grid {
      display: inline-grid;
      grid-template-columns: 1fr 2fr 3fr;
  