Test setting the prototype of a Window to itself.

js/behaviours/SetPrototypeOf-window.html

@@ -5,6 +5,18 @@
 <script src="/resources/testharnessreport.js"></script>
 <div id="log"></div>
 <script>
+test(function() {
+  assert_throws(new TypeError, function() {
+    Object.setPrototypeOf(window, window);
+  }, "Setting the prototype should throw");
+}, "Setting the prototype of a window to itself via setPrototypeOf");
+
+test(function() {
+  assert_throws(new TypeError, function() {
+    window.__proto__ = window;
+  }, "Setting the prototype should throw");
+}, "Setting the prototype of a window to itself via __proto__");
+
 test(function() {
   assert_throws(new TypeError, function() {
     Object.setPrototypeOf(window, Object.create(window));