Improve error reporting for duplicate object template properties.

src/apinatives.js

 // Copyright 2006-2008 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.
 
 "use strict";
 
 // This file contains infrastructure used by the API.  See
 // v8natives.js for an explanation of these files are processed and
 // loaded.
 
@@ skipping 81 matching lines @@
   // Disable access checks while instantiating the object.
   var requires_access_checks = %DisableAccessChecks(obj);
   try {
     for (var i = 1; i < properties[0];) {
       var length = properties[i];
       if (length == 3) {
         var name = properties[i + 1];
         var prop_data = properties[i + 2];
         var attributes = properties[i + 3];
         var value = Instantiate(prop_data, name);
-        %AddProperty(obj, name, value, attributes);
+        %AddPropertyForTemplate(obj, name, value, attributes);
       } else if (length == 4 || length == 5) {
         // TODO(verwaest): The 5th value used to be access_control. Remove once
         // the bindings are updated.
         var name = properties[i + 1];
         var getter = Instantiate(properties[i + 2]);
         var setter = Instantiate(properties[i + 3]);
         var attribute = properties[i + 4];
         %DefineAccessorPropertyUnchecked(obj, name, getter, setter, attribute);
       } else {
         throw "Bad properties array";
       }
       i += length + 1;
     }
   } finally {
     if (requires_access_checks) %EnableAccessChecks(obj);
   }
 }