Yet another unnecessary ElementX reference

tests/compiler/dart2js/serialization/test_data.dart

 // Copyright (c) 2016, 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.
 
 library dart2js.serialization_test_data;
 
 const List<Test> TESTS = const <Test>[
   const Test(const {
     'main.dart': 'main() {}'
   }),
@@ skipping 235 matching lines @@
 main() => new UnmodifiableListView(null);
 ''',
   }),
 
   const Test(const {
     'main.dart': '''
 var myIdentical = identical;
 main() => myIdentical;
 ''',
   }),
+
+  const Test(const {
+    'main.dart': '''
+class Foo {
+  String toString() => super.toString();
+}
+main() {
+  print(new Foo());
+}
+''',
+  }),
 ];
 
 class Test {
   final Map sourceFiles;
   final int expectedErrorCount;
   final int expectedWarningCount;
   final int expectedHintCount;
   final int expectedInfoCount;
 
   const Test(this.sourceFiles, {
     this.expectedErrorCount: 0,
     this.expectedWarningCount: 0,
     this.expectedHintCount: 0,
     this.expectedInfoCount: 0});
 }