Allow Object when doing lookups.

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 61954e6b2ea19e421cbbc46c4698b0d0520d01b1..64326a47df1a2ba87de7b9b046f41bb7f886f5a7 100644
--- a/sdk/lib/html/html_common/filtered_element_list.dart
+++ b/sdk/lib/html/html_common/filtered_element_list.dart
@@ -59,8 +59,10 @@ class FilteredElementList<T extends Element> extends ListBase<T> {
     }
   }
 
-  bool contains(Element element) {
-    return (element != null) && (element.parentNode == _node);
+  bool contains(Object needle) {
+    if (needle is! Element) return false;
+    Element element = needle;
+    return element.parentNode == _node;
   }
 
   Iterable<Element> get reversed => _filtered.reversed;