Add toString to delegating collections in package:collection.

pkg/collection/lib/wrappers.dart

 // Copyright (c) 2013, 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.
 
 /**
  * Delegating wrappers for [Iterable], [List], [Set], [Queue] and [Map].
  *
  * Also adds unmodifiable views for `Set` and `Map`, and a fixed length
  * view for `List`. The unmodifable list view from `dart:collection` is exported
  * as well, just for completeness.
@@ skipping 71 matching lines @@
 
   Iterable<E> take(int n) => _base.take(n);
 
   Iterable<E> takeWhile(bool test(E value)) => _base.takeWhile(test);
 
   List<E> toList({bool growable: true}) => _base.toList(growable: growable);
 
   Set<E> toSet() => _base.toSet();
 
   Iterable<E> where(bool test(E element)) => _base.where(test);
+
+  String toString() => _base.toString();
 }
 
 
 /**
  * Creates a [List] that delegates all operations to a base list.
  *
  * This class can be used hide non-`List` methods of a list object,
  * or it can be extended to add extra functionality on top of an existing
  * list object.
  */
@@ skipping 222 matching lines @@
 
   Iterable<K> get keys => _base.keys;
 
   int get length => _base.length;
 
   V putIfAbsent(K key, V ifAbsent()) => _base.putIfAbsent(key, ifAbsent);
 
   V remove(Object key) => _base.remove(key);
 
   Iterable<V> get values => _base.values;
+
+  String toString() => _base.toString();
 }