Use browsers JSON.parse for parsing JSON (#3)

sdk/lib/json/json_base.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // JSON parsing and serialization.
 
 /**
  * Error thrown by JSON serialization if an object cannot be serialized.
  *
  * The [unsupportedObject] field holds that object that failed to be serialized.
@@ skipping 29 matching lines @@
  * JSON values.
  *
  * The optional [revivier] function, if provided, is called once for each
  * object or list property parsed. The arguments are the property name
  * ([String]) or list index ([int]), and the value is the parsed value.
  * The return value of the revivier will be used as the value of that property
  * instead the parsed value.
  *
  * Throws [FormatException] if the input is not valid JSON text.
  */
-parse(String json, [reviver(var key, var value)]) {
+external parse(String json, [reviver(var key, var value)]);
+
+_parse(String json, reviver(var key, var value)) {
   BuildJsonListener listener;
   if (reviver == null) {
     listener = new BuildJsonListener();
   } else {
     listener = new ReviverJsonListener(reviver);
   }
   new JsonParser(json, listener).parse();
   return listener.result;
 }
 
@@ skipping 732 matching lines @@
         first = false;
       });
       sb.add('}');
       seen.removeLast();
       return true;
     } else {
       return false;
     }
   }
 }