chromium/third_party/blink/web_tests/http/tests/security/lenient-this-issue569043.html

<!DOCTYPE html>
<html>
<iframe name="frame1" src="http://localhost:8000/resources/dummy.html"></iframe>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
"use strict";

test(function() {
  class A {
    inject() {
      try {
        super.onmousedown = Function;  // not [LegacyLenientThis]
        assert_unreached("Accessing to onmousedown on a cross-origin window should throw.");
      } catch (e) {}
      try {
        super.onmouseenter = Function;  // [LegacyLenientThis]
        assert_unreached("Accessing to onmouseenter on a cross-origin window should throw.");
      } catch (e) {}
    }
  }

  A.prototype.__proto__ = window;

  var a = new A();
  a.inject.call(frame1);  // Call with a cross-origin window.
}, "Accessing to a cross-origin window should throw regardless of [LegacyLenientThis].");
</script>
</html>