chromium/third_party/blink/web_tests/external/wpt/css/css-masking/mask-image/mask-image-4a.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>CSS Masking: mask-image: unresovlable mask url</title>
    <link rel="author" title="CJ Ku" href="mailto:[email protected]">
    <link rel="author" title="Mozilla" href="https://www.mozilla.org">
    <link rel="help" href="https://www.w3.org/TR/css-masking-1/#the-mask-image">
    <link rel="match" href="/css/reference/blank.html">
    <meta name="assert" content="Test checks non-existent url should be counted as an image layer of transparent black.">
    <style type="text/css">
      div {
        background-color: purple;
        width: 100px;
        height: 100px;
      }

      div.mask-by-png {
        mask-image: url(non-existent.png);
      }
    </style>
  </head>
  <body>
    <div class="mask-by-png"></div>
  </body>
</html>