Revert "Remove the generics from _FrozenElementList: causes checked mode failures"

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;
 
 class _ChildrenElementList extends ListBase<Element>
     implements NodeListWrapper {
   // Raw Element.
   final Element _element;
@@ skipping 246 matching lines @@
   CssRect get marginEdge;
 $!STREAM_GETTER_SIGNATURES
 }
 
 // Wrapper over an immutable NodeList to make it implement ElementList.
 //
 // Clients are {`Document`, `DocumentFragment`}.`querySelectorAll` which are
 // declared to return `ElementList`.  This provides all the static analysis
 // benefit so there is no need for this class have a constrained type parameter.
 //
-class _FrozenElementList extends ListBase
-    implements ElementList, NodeListWrapper {
+class _FrozenElementList extends ListBase<Element>
+    implements ElementList<Element>, NodeListWrapper {
   final List<Node> _nodeList;
 
 $if JSINTEROP
   var dartClass_instance;
 
   _FrozenElementList._wrap(this._nodeList) {
       this.dartClass_instance = this._nodeList;
   }
 $else
   _FrozenElementList._wrap(this._nodeList);
@@ skipping 1244 matching lines @@
     return result;
   }
 $else
   static String _safeTagName(element) {
     try {
       // Safe as we plumb directly to a C++ native method.
       return element.tagName;
     } catch (e) {}
     return 'element tag unavailable';
   }
-$endif
+$endif  
 
 $if DART2JS
   @DomName('Element.offsetParent')
   @DocsEditable()
   final Element offsetParent;
 
   @DomName('Element.offsetHeight')
   @DocsEditable()
   int get offsetHeight => JS('num', '#.offsetHeight', this).round();
 
@@ skipping 125 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');
 }