Do proper security checks when accessing elements with getOwnPropertyDescriptor.

test/mjsunit/get-own-property-descriptor.js

 // Copyright 2010 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 85 matching lines @@
 
 // Test that elements in the prototype chain is not returned.
 var proto = {};
 proto[10] = 42;
 
 var objWithProto = new Array();
 objWithProto.prototype = proto;
 objWithProto[0] = 'bar';
 var descWithProto = Object.getOwnPropertyDescriptor(objWithProto, '10');
 assertEquals(undefined, descWithProto);
+
+// Test elements on global proxy object.
+var global = (function() { return this; })();
+
+global[42] = 42;
+
+function el_getter() { return 239; };
+function el_setter() {};
+Object.defineProperty(global, '239', {get: el_getter, set: el_setter});
+
+var descRegularElement = Object.getOwnPropertyDescriptor(global, '42');
+assertEquals(42, descRegularElement.value);
+
+var descAccessorElement = Object.getOwnPropertyDescriptor(global, '239');
+assertEquals(el_getter, descAccessorElement.get);
+assertEquals(el_setter, descAccessorElement.set);