Use premordial Object.isSealed/isFrozen in builtins.

test/mjsunit/regress/regress-builtinbust-1.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+function nope() { return false; }
+var a = [ 1, 2, 3 ];
+Object.seal(a);
+Object.isSealed = nope;
+
+assertThrows(function() { a.pop(); }, TypeError);
+assertThrows(function() { a.push(5); }, TypeError);
+assertThrows(function() { a.shift(); }, TypeError);
+assertThrows(function() { a.unshift(5); }, TypeError);
+assertThrows(function() { a.splice(0, 1); }, TypeError);