Add List.shuffle().

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 5732c1ebd5469464a8cdc917a75156394a97d705..5494ca8ca4b4634a7064e5337d4381e60c7feffd 100644
--- a/tools/dom/templates/html/impl/impl_Element.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Element.darttemplate
@@ -58,6 +58,10 @@ class _ChildrenElementList extends ListBase<Element> {
     throw new UnsupportedError('Cannot sort element lists');
   }
 
+  void shuffle() {
+    throw new UnsupportedError('Cannot shuffle element lists');
+  }
+
   void removeWhere(bool test(Element element)) {
     _filter(test, false);
   }
@@ -276,6 +280,10 @@ class _FrozenElementList<T extends Element> extends ListBase<T> implements Eleme
     throw new UnsupportedError('Cannot sort list');
   }
 
+  void shuffle() {
+    throw new UnsupportedError('Cannot shuffle list');
+  }
+
   Element get first => _nodeList.first;
 
   Element get last => _nodeList.last;