Introduce InternalPackedArray.

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 49 matching lines @@
     return unfiltered;
   }
 }
 
 function SerializeArray(value, replacer, stack, indent, gap) {
   if (!%PushIfAbsent(stack, value)) {
     throw MakeTypeError('circular_structure', $Array());
   }
   var stepback = indent;
   indent += gap;
-  var partial = new InternalArray();
+  var partial = new InternalPackedArray();
   var len = value.length;
   for (var i = 0; i < len; i++) {
     var strP = JSONSerialize($String(i), value, replacer, stack,
                              indent, gap);
     if (IS_UNDEFINED(strP)) {
       strP = "null";
     }
     partial.push(strP);
   }
   var final;
   if (gap == "") {
     final = "[" + partial.join(",") + "]";
   } else if (partial.length > 0) {
     var separator = ",\n" + indent;
     final = "[\n" + indent + partial.join(separator) + "\n" +
         stepback + "]";
   } else {
     final = "[]";
   }
   stack.pop();
   return final;
 }
 
 function SerializeObject(value, replacer, stack, indent, gap) {
   if (!%PushIfAbsent(stack, value)) {
     throw MakeTypeError('circular_structure', $Array());
   }
   var stepback = indent;
   indent += gap;
-  var partial = new InternalArray();
+  var partial = new InternalPackedArray();
   if (IS_ARRAY(replacer)) {
     var length = replacer.length;
     for (var i = 0; i < length; i++) {
       if (%_CallFunction(replacer, i, ObjectHasOwnProperty)) {
         var p = replacer[i];
         var strP = JSONSerialize(p, value, replacer, stack, indent, gap);
         if (!IS_UNDEFINED(strP)) {
           var member = %QuoteJSONString(p) + ":";
           if (gap != "") member += " ";
           member += strP;
@@ skipping 106 matching lines @@
 
 
 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, void 0, new InternalArray(), "", "");
 }
 
 SetUpJSON();