chromium/third_party/blink/web_tests/svg/custom/non-circular-marker-reference.svg

<?xml version="1.0" encoding="ISO-8859-1"?>

<svg xmlns="http://www.w3.org/2000/svg" viewBox="-10 -10 20 20"
  stroke="#000" stroke-linecap="round">

  <defs>
    <marker id="mark" viewBox="0 0 8 8" refX="4" refY="4" markerWidth="3" markerHeight="3">
      <circle cx="4" cy="4" r="3" stroke="#ff0000" fill="none"/>
    </marker>
  </defs>

  <path d="M-5,-2h5h5"/>
  <path d="M-5,+2h5h5"
    marker-start="url(#mark)" marker-mid="url(#mark)" marker-end="url(#mark)"/>

</svg>