Wrote functions to convert collections and maps to strings and invoked

corelib/src/implementation/splay_tree.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
 /**
  * A node in a splay tree. It holds the key, the value and the left
  * and right children in the tree.
  */
 class SplayTreeNode<K, V> {
   SplayTreeNode(K k, V v) {
     key = k;
@@ skipping 215 matching lines @@
     List<K> list = new List<K>();
     forEach((K k, V v) { list.add(k); });
     return list;
   }
 
   Collection<V> getValues() {
     List<V> list = new List<V>();
     forEach((K k, V v) { list.add(v); });
     return list;
   }
+
+  String toString() {
+    return Maps.mapToString(this);
+  }
 }