Make html lists print a nice toString method.

tools/dom/src/WrappedList.dart

Index: tools/dom/src/WrappedList.dart
diff --git a/tools/dom/src/WrappedList.dart b/tools/dom/src/WrappedList.dart
index 171dd7e49c8323735d4b13cfde4987b2b4ad6fa5..d0c80031b642ff95a77ca64665fa31683a63ca5c 100644
--- a/tools/dom/src/WrappedList.dart
+++ b/tools/dom/src/WrappedList.dart
@@ -131,6 +131,13 @@ class _WrappedList<E> implements List<E> {
   }
 
   Map<int, E> asMap() => IterableMixinWorkaround.asMapList(_list);
+
+  String toString() {
+    StringBuffer buffer = new StringBuffer('[');
+    buffer.writeAll(this, ', ');
+    buffer.write(']');
+    return buffer.toString();
+  }
 }
 
 /**