Fix issues with JSON stringify replacer array

src/json.js

 // Copyright 2009 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 195 matching lines @@
       gap = %_SubString(space, 0, 10);
     } else {
       gap = space;
     }
   } else {
     gap = "";
   }
   if (IS_ARRAY(replacer)) {
     // Deduplicate replacer array items.
     var property_list = new InternalArray();
-    var seen_properties = {};
+    var seen_properties = { __proto__: null };
+    var seen_sentinel = {};
     var length = replacer.length;
     for (var i = 0; i < length; i++) {
       var item = replacer[i];
-      if (IS_NUMBER(item)) item = %_NumberToString(item);
-      if (IS_STRING(item) && !(item in seen_properties)) {
+      if (IS_STRING_WRAPPER(item)) {
+        item = ToString(item);
+      } else {
+        if (IS_NUMBER_WRAPPER(item)) item = ToNumber(item);
+        if (IS_NUMBER(item)) item = %_NumberToString(item);
+      }
+      if (IS_STRING(item) && seen_properties[item] != seen_sentinel) {
         property_list.push(item);
-        seen_properties[item] = true;
+        // We cannot use true here because __proto__ needs to be an object.
+        seen_properties[item] = seen_sentinel;
       }
     }
     replacer = property_list;
   }
   return JSONSerialize('', {'': value}, replacer, new InternalArray(), "", gap);
 }
 
 
 // -------------------------------------------------------------------
 
@@ skipping 12 matching lines @@
 
 // -------------------------------------------------------------------
 // JSON Builtins
 
 function JSONSerializeAdapter(key, object) {
   var holder = {};
   holder[key] = object;
   // No need to pass the actual holder since there is no replacer function.
   return JSONSerialize(key, holder, UNDEFINED, new InternalArray(), "", "");
 }