chromium/chrome/test/data/extensions/declarative_net_request/image.html

<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
imageCollapsed = false;
window.addEventListener('load', () => {
  var image = document.getElementById('image');
  var display = window.getComputedStyle(image).display;
  imageCollapsed = display == 'none';
});
</script>
</head>

<body>
  <img src="subresources/image.png" id="image" >
</body>

</html>