Remove the generics from _FrozenElementList: causes checked mode failures

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

Index: tools/dom/templates/html/impl/impl_Element.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_Element.darttemplate b/tools/dom/templates/html/impl/impl_Element.darttemplate
index 886ceb049e7b1886777978db79a931eb0953db4d..fd4fae2f01c9926ff9870dad31e7663ed70c4a46 100644
--- a/tools/dom/templates/html/impl/impl_Element.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Element.darttemplate
@@ -264,8 +264,8 @@ $!STREAM_GETTER_SIGNATURES
 // 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<Element>
-    implements ElementList<Element>, NodeListWrapper {
+class _FrozenElementList extends ListBase
+    implements ElementList, NodeListWrapper {
   final List<Node> _nodeList;
 
 $if JSINTEROP
@@ -1531,7 +1531,7 @@ $else
     } catch (e) {}
     return 'element tag unavailable';
   }
-$endif  
+$endif
 
 $if DART2JS
   @DomName('Element.offsetParent')