chromium/third_party/blink/web_tests/media/video-default-poster.html

<!DOCTYPE html>
<html>
<head>
<script>
  if (window.testRunner) {
    testRunner.dumpAsText();
    testRunner.waitUntilDone();
  }
  if (window.internals) {
    var default_poster = 'content/greenbox.png';
    internals.settings.setDefaultVideoPosterURL(default_poster);
    addEventListener("load", function() {
      var poster = internals.getImageSourceURL(document.getElementById("video-no-poster"));
      if (poster) {
        if (poster == default_poster)
          document.getElementById("result-no-poster").innerText = "PASS";
        else
          document.getElementById("result-no-poster").innerText = "FAIL";
      } else
        document.getElementById("result-no-poster").innerText = "FAIL: image source is null";

      poster =  internals.getImageSourceURL(document.getElementById("video-has-poster"));
      if (poster) {
        if (poster == "content/abe.png")
          document.getElementById("result-has-poster").innerText = "PASS";
        else
          document.getElementById("result-has-poster").innerText = "FAIL: poster was changed";
      } else
        document.getElementById("result-has-poster").innerText = "FAIL: image source is null";

      poster =  internals.getImageSourceURL(document.getElementById("video-has-empty-poster"));
      if (poster) {
        if (poster == default_poster)
          document.getElementById("result-has-empty-poster").innerText = "PASS";
        else
          document.getElementById("result-has-empty-poster").innerText = "FAIL";
      } else
        document.getElementById("result-has-empty-poster").innerText = "FAIL: image source is null";

      testRunner.notifyDone();
    }, false);
  }

</script>
</head>
<body>
<pre id="result-no-poster"></pre>
<pre id="result-has-poster"></pre>
<pre id="result-has-empty-poster"></pre>
<video id="video-no-poster" src="content/test.mp4" preload="none" />
<video id="video-has-poster" src="content/test.mp4" poster="content/abe.png" preload="none" />
<video id="video-has-empty-poster" src="content/test.mp4" poster="" preload="none" />
</body>
</html>