Add List.insert.

tools/dom/templates/html/impl/impl_Element.darttemplate

 // Copyright (c) 2012, 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.
 
 part of $LIBRARYNAME;
 
 // TODO(jacobr): use _Lists.dart to remove some of the duplicated
 // functionality.
 class _ChildrenElementList implements List {
   // Raw Element.
@@ skipping 196 matching lines @@
 
   int indexOf(Element element, [int start = 0]) {
     return Lists.indexOf(this, element, start, this.length);
   }
 
   int lastIndexOf(Element element, [int start = null]) {
     if (start == null) start = length - 1;
     return Lists.lastIndexOf(this, element, start);
   }
 
+  void insert(int index, Element element) {
+    if (index < 0 || index > length) throw RangeError(index);
+    if (index == length) {
+      _element.$dom_appendChild(element);
+    } else {
+      throw new UnimplementedError("insert on ElementLists");

[Lasse Reichstein Nielsen, 2013/03/07 09:57:53]

Can you use:
 _element.$dom_insertBefore(element, _childElements[index]);
?

[floitsch, 2013/03/07 12:53:53]

No. doesn't exist in Dart yet. That's why I added Pete as reviewer.

[blois, 2013/03/08 02:32:40]

I would leave this as unsupported for now. I can investigate  implementing.
insertBefore doesn't quite fit as it deals with nodes which are a superset of
elements.

+    }
+  }
+
   void clear() {
     // It is unclear if we want to keep non element nodes?
     _element.text = '';
   }
 
   Element removeAt(int index) {
     final result = this[index];
     if (result != null) {
       _element.$dom_removeChild(result);
     }
@@ skipping 896 matching lines @@
   const ScrollAlignment._internal(this._value);
   toString() => 'ScrollAlignment.$_value';
 
   /// Attempt to align the element to the top of the scrollable area.
   static const TOP = const ScrollAlignment._internal('TOP');
   /// Attempt to center the element in the scrollable area.
   static const CENTER = const ScrollAlignment._internal('CENTER');
   /// Attempt to align the element to the bottom of the scrollable area.
   static const BOTTOM = const ScrollAlignment._internal('BOTTOM');
 }