Better ability to have hand-written custom rules and various cleanups.

pkg/serialization/lib/src/serialization_helpers.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.
 
 /**
  * This contains extra functions and classes useful for implementing
  * serialiation. Some or all of these will be removed once the functionality is
  * available in the core library.
  */
 library serialization_helpers;
@@ skipping 182 matching lines @@
 
   putIfAbsent(key, ifAbsent) => super.putIfAbsent(wrap(key), ifAbsent);
 
   containsKey(key) => super.containsKey(wrap(key));
   forEach(f) => super.forEach((key, value) => f(unwrap(key), value));
   remove(key) => super.remove(unwrap(key));
   /**
    * Note that keys is a very inefficient operation for this type. Don't do it.
    */
   get keys => super.keys.map((x) => unwrap(x));
-}
-
-
+}