chromium/third_party/blink/web_tests/svg/custom/inline-style-overrides-mask.svg

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
    <style type="text/css"><![CDATA[
      #rect {
        fill: green;
        mask: url(#mask);
      }
      ]]>
    </style>
  <defs>
    <mask id="mask" maskUnits="userSpaceOnUse" x="0" y="0" width="100" height="100">
      <rect x="0" y="0" width="100" height="100" fill="black"/>
    </mask>
  </defs>

  <rect width="100" height="100" style="fill: red;" />
  <rect id="rect" width="100" height="100" style="mask: none;" />
</svg>