<!doctype html>
<html>
<head>
<meta charset=utf-8>
<script>
Element.prototype.animate = function() {
  throw 'Called animate() as defined in content document';
}
for (let name of ["KeyframeEffect", "Animation"]) {
  this[name] = function() {
    throw `Called overridden ${name} constructor`;
  };
}
</script>
<body>
<div id="target"></div>
</body>
</html>
