Reinstall previous behavior for Set and Queue toString.

runtime/lib/growable_array.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.
 
 class _GrowableList<T> implements List<T> {
   static final int _classId = (new _GrowableList(0))._cid;
 
   void insert(int index, T element) {
     if (index < 0 || index > length) {
       throw new RangeError.range(index, 0, length);
@@ skipping 309 matching lines @@
   Iterable<T> get reversed => IterableMixinWorkaround.reversedList(this);
 
   void sort([int compare(T a, T b)]) {
     IterableMixinWorkaround.sortList(this, compare);
   }
 
   void shuffle([Random random]) {
     IterableMixinWorkaround.shuffleList(this, random);
   }
 
-  String toString() {
-    return IterableMixinWorkaround.toStringIterable(this, '[', ']');
-  }
+  String toString() => ListBase.listToString(this);
 
   Iterator<T> get iterator {
     return new ListIterator<T>(this);
   }
 
   List<T> toList({ bool growable: true }) {
     return new List<T>.from(this, growable: growable);
   }
 
   Set<T> toSet() {
     return new Set<T>.from(this);
   }
 
   Map<int, T> asMap() {
     return IterableMixinWorkaround.asMapList(this);
   }
 }