Reland "Clean up after r16292 (disable optimization for StringWrappers)."

test/mjsunit/regress/regress-2855.js

 // Copyright 2013 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 21 matching lines @@
 }
 
 var expected = "hello";
 for (var i = 0; i < 4; ++i) {
   if (i == 2) {
     String.prototype.valueOf = function() { return 42; }
     expected = "42";
   }
   assertEquals(expected, "" + foo("hello"));
 }
+
+// Make sure we look up "valueOf" only once.
+var count = 0;
+var x = new String("foo");
+Object.defineProperty(x, "valueOf",
+    { get: function() {
+             count++;
+             return function() {
+                      return 11;
+                    }
+           }
+    });
+for (var i = 0; i < 3; i++) {
+  assertEquals("11", "" + x);
+  assertEquals(i + 1, count);
+}