Indices passed to FilteredElementList public functions should consistently refer to element indices

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 3514cdc654135ce42502eb59c6f95fe81e9a0355..242da062ca615ee136ab7f6577f99b6aeb35487c 100644
--- a/sdk/lib/html/html_common/filtered_element_list.dart
+++ b/sdk/lib/html/html_common/filtered_element_list.dart
@@ -28,8 +28,8 @@ class FilteredElementList<T extends Element> extends ListBase<T>
   //
   // TODO(nweiz): we don't always need to create a new list. For example
   // forEach, every, any, ... could directly work on the _childNodes.
-  List<T> get _filtered =>
-    new List<T>.from(_childNodes.where((n) => n is Element));
+  Iterable<T> get _iterable => _childNodes.where((n) => n is Element);
+  List<T> get _filtered => new List<T>.from(_iterable, growable: false);
 
   void forEach(void f(T element)) {
     _filtered.forEach(f);
@@ -104,11 +104,13 @@ class FilteredElementList<T extends Element> extends ListBase<T>
   }
 
   void insert(int index, T value) {
-    _childNodes.insert(index, value);
+    Element element =_iterable.elementAt(index);
+    element.parentNode.insertBefore(value, element);
   }
 
   void insertAll(int index, Iterable<T> iterable) {
-    _childNodes.insertAll(index, iterable);
+    Element element =_iterable.elementAt(index);
+    element.parentNode.insertAllBefore(iterable, element);
   }
 
   T removeAt(int index) {