Added new version of reduce.

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 ed8e12dc0234cab431cd995c0ce666898428af76..f915f8208e229b4be2fbb3464e085b5f962c82f1 100644
--- a/sdk/lib/html/html_common/filtered_element_list.dart
+++ b/sdk/lib/html/html_common/filtered_element_list.dart
@@ -141,14 +141,13 @@ class FilteredElementList extends ListBase<Element> {
     IterableMixinWorkaround.retainWhere(this, test);
   }
 
-  dynamic reduce(dynamic initialValue,
-      dynamic combine(dynamic previousValue, Element element)) {
-    return _filtered.reduce(initialValue, combine);
+  Element reduce(Element combine(Element value, Element element)) {
+    return _filtered.reduce(combine);
   }
 
   dynamic fold(dynamic initialValue,
       dynamic combine(dynamic previousValue, Element element)) {
-    return IterableMixinWorkaround.fold(this, initialValue, combine);
+    return _filtered.fold(initialValue, combine);
   }
 
   bool every(bool f(Element element)) => _filtered.every(f);