Fixing polyfill for Element.createShadowRoot.

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> {
   // Raw Element.
   final Element _element;
   final HtmlCollection _childElements;
@@ skipping 887 matching lines @@
   Element _templateInstanceRef;
 
   // Note: only used if `this is! TemplateElement`
 $if DART2JS
   @Creates('Null')  // Set from Dart code; does not instantiate a native type.
 $endif
   DocumentFragment _templateContent;
 
   bool _templateIsDecorated;
 
+$if DART2JS
+  @DomName('Element.createShadowRoot')
+  @SupportedBrowser(SupportedBrowser.CHROME, '25')
+  @Experimental()
+  ShadowRoot createShadowRoot() {
+    return JS('ShadowRoot',
+      '(#.createShadowRoot || #.webkitCreateShadowRoot).call(#)',
+      this, this, this);
+  }
+$endif
+
 
   /**
    * Gets the template this node refers to.
    * This is only supported if [isTemplate] is true.
    */
   @Experimental()
   Element get ref {
     _ensureTemplate();
 
     Element result = null;
@@ skipping 367 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');
 }