Add List.reversed to give a reverse fixed-length view of a list.

sdk/lib/html/html_common/filtered_element_list.dart

Index: sdk/lib/html/html_common/filtered_element_list.dart
diff --git a/sdk/lib/html/html_common/filtered_element_list.dart b/sdk/lib/html/html_common/filtered_element_list.dart
index 44768c4fcacfe18698896ff9e4e59a48f3d16fcc..d90ae656e36daf4bb4255dc8c9f70b6bcc4df9ae 100644
--- a/sdk/lib/html/html_common/filtered_element_list.dart
+++ b/sdk/lib/html/html_common/filtered_element_list.dart
@@ -69,6 +69,8 @@ class FilteredElementList implements List {
     return element is Element && _childNodes.contains(element);
   }
 
+  List<E> get reversed => new ReversedList<E>(_filtered, 0, length);
+
   void sort([int compare(Element a, Element b)]) {
     throw new UnsupportedError('TODO(jacobr): should we impl?');
   }