Make html lists print a nice toString method.

tools/dom/templates/html/impl/impl_Node.darttemplate

 // 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.
 
 part of $LIBRARYNAME;
 
 /**
  * Lazy implementation of the child nodes of an element that does not request
  * the actual child nodes of an element until strictly necessary greatly
  * improving performance for the typical cases where it is not required.
@@ skipping 234 matching lines @@
         "Cannot insertRange on immutable List.");
   }
   List<Node> sublist(int start, [int end]) {
     if (end == null) end == length;
     return Lists.getRange(this, start, end, <Node>[]);
   }
 
   List<Node> getRange(int start, int rangeLength) =>
       sublist(start, start + rangeLength);
 
+  String toString() {
+    StringBuffer buffer = new StringBuffer('[');
+    buffer.writeAll(this, ', ');
+    buffer.write(']');
+    return buffer.toString();
+  }
   // -- end List<Node> mixins.
 
   // TODO(jacobr): benchmark whether this is more efficient or whether caching
   // a local copy of $dom_childNodes is more efficient.
   int get length => _this.$dom_childNodes.length;
 
   void set length(int value) {
     throw new UnsupportedError(
         "Cannot set length on immutable List.");
   }
@@ skipping 148 matching lines @@
     if (_modelChangedStream == null) {
       // Ensure the model is cached locally to minimize change notifications.
       _model = model;
       _modelChangedStream = new StreamController.broadcast();
     }
     return _modelChangedStream.stream;
   }
 
 $!MEMBERS
 }