Check global object behind global proxy for extensibility

test/mjsunit/regress/regress-crbug-454091.js

Index: test/mjsunit/regress/regress-crbug-454091.js
diff --git a/test/mjsunit/compiler/regress-451012.js b/test/mjsunit/regress/regress-crbug-454091.js
similarity index 51%
copy from test/mjsunit/compiler/regress-451012.js
copy to test/mjsunit/regress/regress-crbug-454091.js
index bffc8bc5bdfac32bb561a24153d00157b26ac3a5..2705e96bfd023f415cd5a7076017900cd251793c 100644
--- a/test/mjsunit/compiler/regress-451012.js
+++ b/test/mjsunit/regress/regress-crbug-454091.js
@@ -2,11 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-"use strict";
-function f() {
-  for (let v; v; ) {
-    let x;
-  }
-}
-
-f();
+this.__proto__ = Array.prototype;
+Object.freeze(this);
+this.length = 1;
+assertThrows('this.__proto__ = {}');
+assertEquals(Array.prototype, this.__proto__);