Fix for v8:3255 Grow KeyedStoreIC doesn't respect String value wrappers

test/mjsunit/regress/regress-3255.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.
+
+// Flags: --allow-natives-syntax --enable-slow-asserts
+
+var arr = [];
+var str = new String('x');
+
+function f(a,b) {
+  a[b] = 1;
+}
+
+f(arr, 0);
+f(str, 0);
+f(str, 0);
+print(str);

[Michael Starzinger, 2014/04/04 16:41:26]

nit: The "print" seems obsolete.

+
+// This is just to trigger elements validation, object already broken.
+%SetProperty(str, 1, 'y', 0);