Tweak toString() for better type inference

tools/dom/templates/html/impl/impl_Element.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;
 
 class _ChildrenElementList extends ListBase<Element>
     implements NodeListWrapper {
   // Raw Element.
   final Element _element;
@@ skipping 795 matching lines @@
   // Note: return type is `dynamic` for convenience to suppress warnings when
   // members of the component are used. The actual type is a subtype of Element.
   get xtag => _xtag != null ? _xtag : this;
 
   void set xtag(Element value) {
     _xtag = value;
   }
 
   @DomName('Element.localName')
   @DocsEditable()
+$if DART2JS
+  @Returns('String')
+  // Non-null for Elements.
+  String get localName => JS('String', '#', _localName);
+$else
   String get localName => _localName;
+$endif
 
   /**
    * A URI that identifies the XML namespace of this element.
    *
    * `null` if no namespace URI is specified.
    *
    * ## Other resources
    *
    * * [Node.namespaceURI]
    * (http://www.w3.org/TR/DOM-Level-3-Core/core.html#ID-NodeNSname) from W3C.
@@ skipping 661 matching lines @@
   const ScrollAlignment._internal(this._value);
   toString() => 'ScrollAlignment.$_value';
 
   /// Attempt to align the element to the top of the scrollable area.
   static const TOP = const ScrollAlignment._internal('TOP');
   /// Attempt to center the element in the scrollable area.
   static const CENTER = const ScrollAlignment._internal('CENTER');
   /// Attempt to align the element to the bottom of the scrollable area.
   static const BOTTOM = const ScrollAlignment._internal('BOTTOM');
 }