third_party/WebKit/LayoutTests/mhtml/cid_in_html_iframe.html

<script>
  if (window.testRunner)
    testRunner.dumpAsText();
</script>
<iframe src="cid:xxxxxx"></iframe>
<p>
  No Content-ID url are expected outside of an MHTML document.
  The document should load without crashing.
</p>