Add new method to Custom Element.

pkg/custom_element/lib/custom_element.dart

 // 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.
 
 /**
  * Custom Elements let authors define their own elements. Authors associate code
  * with custom tag names, and then use those custom tag names as they would any
  * standard tag. See <www.polymer-project.org/platform/custom-elements.html>
  * for more information.
  */
@@ skipping 379 matching lines @@
   void scrollByPages(int pages) {
     host.scrollByPages(pages);
   }
 
   void scrollIntoView([ScrollAlignment alignment]) {
     host.scrollIntoView(alignment);
   }
 
   bool matches(String selectors) => host.matches(selectors);
 
+  bool matchesWithAncestors(String selectors) =>
+      host.matchesWithAncestors(selectors);
+
   @deprecated
   void requestFullScreen(int flags) { requestFullscreen(); }
 
   void requestFullscreen() { host.requestFullscreen(); }
 
   void requestPointerLock() { host.requestPointerLock(); }
 
   Element query(String selectors) => host.query(selectors);
 
   ElementList queryAll(String selectors) => host.queryAll(selectors);
@@ skipping 246 matching lines @@
       for (var removed in record.removedNodes) {
         if (identical(node, removed)) {
           observer.disconnect();
           element.removed();
           return;
         }
       }
     }
   }).observe(element.parentNode, childList: true);
 }