Fix bogus Object.isSealed check in some Array builtins.

test/mjsunit/regress/regress-builtinbust-4.js

Index: test/mjsunit/regress/regress-builtinbust-4.js
diff --git a/test/mjsunit/regress/regress-builtinbust-4.js b/test/mjsunit/regress/regress-builtinbust-4.js
new file mode 100644
index 0000000000000000000000000000000000000000..dbaa2454daf3a6dcb71bd578e3c67226c81abc32
--- /dev/null
+++ b/test/mjsunit/regress/regress-builtinbust-4.js
@@ -0,0 +1,16 @@
+// 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.
+
+var o = { __proto__:Array.prototype, 0:"x" };
+function boomer() { return 0; }
+Object.defineProperty(o, "length", { get:boomer, set:boomer });
+Object.seal(o);
+
+assertDoesNotThrow(function() { o.push(1); });
+assertEquals(0, o.length);
+assertEquals(1, o[0]);
+
+assertDoesNotThrow(function() { o.unshift(2); });
+assertEquals(0, o.length);
+assertEquals(2, o[0]);