Move kernel baseline tests to front_end.

pkg/front_end/testcases/rasta/issue_000053.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.md file.
 
 class C {
   operator ==(other) => throw 'x';
   test() {
     super == null;
   }
 }
 main() {
   new C().test();
 }