<!DOCTYPE html>
<html lang="en-US">
<head>
</head>
<body>
<x-foo></x-foo>
<script>
var prototype = Object.create(HTMLElement.prototype);
prototype.createdCallback = function() {
createdCallbackCalled = true;
}
document.registerElement('x-foo', {prototype: prototype});
</script>
</body>
</html>