Revert "Make window.{undefined,NaN,Infinity} read-only"

test/mjsunit/undeletable-functions.js

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 58 matching lines @@
 array = [
   "E", "LN10", "LN2", "LOG2E", "LOG10E", "PI", "SQRT1_2", "SQRT2"];
 CheckDontDelete(Math, array, "Math2");
 
 array = [
   "escape", "unescape", "decodeURI", "decodeURIComponent", "encodeURI",
   "encodeURIComponent", "isNaN", "isFinite", "parseInt", "parseFloat", "eval",
   "execScript"];
 CheckEcmaSemantics(this, array, "Global");
 CheckReadOnlyAttr(this, "Infinity");
-CheckReadOnlyAttr(this, "NaN");
-CheckReadOnlyAttr(this, "undefined");
 
 array = ["exec", "test", "toString", "compile"];
 CheckEcmaSemantics(RegExp.prototype, array, "RegExp prototype");
 
 array = [
   "toString", "toLocaleString", "valueOf", "hasOwnProperty",
   "isPrototypeOf", "propertyIsEnumerable", "__defineGetter__",
   "__lookupGetter__", "__defineSetter__", "__lookupSetter__"];
 CheckEcmaSemantics(Object.prototype, array, "Object prototype");
 
@@ skipping 93 matching lines @@
 
 
 function CheckReadOnlyAttr(type, prop) {
   var old = type[prop];
   if (!type[prop]) return;
   assertTrue(type.hasOwnProperty(prop), "inherited: " + prop);
   var deleted = delete type[prop];
   assertFalse(deleted, "delete operator returned true: " + prop);
   assertTrue(type.hasOwnProperty(prop), "not there after delete: " + prop);
   type[prop] = "foo";
-  assertEquals(old, type[prop], "overwritable: " + prop);
+  assertEquals("foo", type[prop], "overwritable: " + prop);
 }
 
 print("OK");