LayoutTests/fetch/header-constructor-subclass.html

<!DOCTYPE HTML>
<html>
<head>
<script src="../resources/js-test-pre.js"></script>
</head>
<body>
<script>
description("This test should create a Headers from an object which is a subclass of Headers.");

let SpecialHeaders = class SpecialHeaders extends Headers {
    constructor() {
        super(...arguments);
    }
};

let specialHeaders = new SpecialHeaders({"a": "1"});
let otherHeaders = new Headers(specialHeaders);
shouldBeEqualToString("otherHeaders.get('a')", "1");

</script>
<script src="../resources/js-test-post.js"></script>
</body>
</html>