css/css-scoping/whitespace-crash-001.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Scoping: Dynamic shadow root creation and whitespace optimization crash.</title>
<link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io">
<link rel="help" href="https://drafts.csswg.org/css-scoping/#selectors-data-model">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1465572">
<link rel="match" href="reference/green-box.html"/>
<p>Test passes if you see a single 100px by 100px green box below.</p>
<!--
  It's important for the test-case that there's whitespace inside the host,
  and that it's not assigned to any slot.
-->
<div id="host">
  <div style="display: inline" slot="the-slot"></div>
</div>
<script>
  // Flush layout before creating a ShadowRoot, so that the whitespace ends up
  // suppressed.
  document.body.offsetTop;
  host.attachShadow({ mode: "open" }).innerHTML = `
    <style>
      ::slotted(div) {
        width: 100px;
        height: 100px;
        background: green;
      }
    </style>
    <slot name="the-slot"></slot>
  `;
  document.body.offsetTop;
  host.firstElementChild.style.display = "block"; // or anything else that reframes the <div>.
</script>