Don't use _toList on FrozenElementList.

client/html/src/ElementWrappingImplementation.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.
 
 // TODO(jacobr): use Lists.dart to remove some of the duplicated functionality.
 class _ChildrenElementList implements ElementList {
   // Raw Element.
   final _element;
   final _childElements;
 
@@ skipping 115 matching lines @@
     return last;
   }
 
   Element last() {
     return LevelDom.wrapElement(_element.lastElementChild);
   }
 }
 
 class FrozenElementList implements ElementList {
   final _ptr;
-  List<Element> _list;
 
   FrozenElementList._wrap(this._ptr);
 
-  List<Element> _toList() {
-    if (_list == null) {
-      _list = new List(_ptr.length);
-      for (int i = 0, len = _ptr.length; i < len; i++) {
-        _list[i] = LevelDom.wrapElement(_ptr[i]);
-      }
-    }
-    return _list;
-  }
-
   Element get first() {
     return this[0];
   }
 
-  void forEach(void f(Element element)) => _toList().forEach(f);
+  void forEach(void f(Element element)) {
+    for (Element el in this) {
+      f(el);
+    }
+  }
 
-  Collection map(f(Element element)) => _toList().map(f);
+  Collection map(f(Element element)) {
+    var out = [];
+    for (Element el in this) {
+      out.add(f(el));
+    }
+    return out;
+  }
 
-  Collection<Element> filter(bool f(Element element)) => _toList().filter(f);
+  Collection<Element> filter(bool f(Element element)) {
+    var out = [];
+    for (Element el in this) {
+      if (f(el)) out.add(el);
+    }
+    return out;
+  }
 
   bool every(bool f(Element element)) {
     for(Element element in this) {
       if (!f(element)) {
         return false;
       }
     };
     return true;
   }
 
@@ skipping 592 matching lines @@
 
   ElementEvents get on() {
     if (_on === null) {
       _on = new ElementEventsImplementation._wrap(_ptr);
     }
     return _on;
   }
 
   Element clone(bool deep) => super.clone(deep);
 }