Fixing DataTransferItemList List<> behavior

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

-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
 part of $LIBRARYNAME;
 
 @DocsEditable()
 $(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$MIXINS$IMPLEMENTS$NATIVESPEC {
 $!MEMBERS
 
+  DataTransferItem operator[] (int index) {
 $if DART2JS
-  void appendRule(String rule) {
-    if (JS('bool', '("appendRule" in #)', this)) {
-      JS('', '#.appendRule(#)', this, rule);
-    } else {
-      JS('', '#.insertRule(#)', this, rule);
-    }
+    return JS('DataTransferItem', '#[#]', this, index);
+$else
+    return __getter__(index);
+$endif
   }
-$endif
+
 }