Specify the types for Element.classes, Element.elements and Node.nodes

client/html/src/DocumentFragmentWrappingImplementation.dart

 // Copyright (c) 2011, 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.
 
 class FilteredElementList implements ElementList {
   final Node _node;
   final NodeList _childNodes;
 
   FilteredElementList(Node node): _childNodes = node.nodes, _node = node;
 
@@ skipping 175 matching lines @@
     return fragment;
   }
 
   ElementList get elements() {
     if (_elements == null) {
       _elements = new FilteredElementList(this);
     }
     return _elements;
   }
 
-  // TODO: The type of value should be Collection<Element>. See http://b/5392897
-  void set elements(value) {
+  void set elements(Collection<Element> value) {
     // Copy list first since we don't want liveness during iteration.
     List copy = new List.from(value);
     final elements = this.elements;
     elements.clear();
     elements.addAll(copy);
   }
 
   String get innerHTML() {
     var e = new Element.tag("div");
     e.nodes.add(this.clone(true));
@@ skipping 181 matching lines @@
       "Title can't be set for document fragments.");
   }
 
   void set webkitdropzone(String value) {
     throw new UnsupportedOperationException(
       "WebKit drop zone can't be set for document fragments.");
   }
 
   DocumentFragment clone(bool deep) => super.clone(deep);
 }