Migrate block 116.

tests/language_2/if_null_assignment_helper.dart

 // Copyright (c) 2015, 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 used by if_null_assignment_behavior_test.dart, which
 // imports it using the prefix "h.".
 
 library lib;
 
 import "package:expect/expect.dart";
@@ skipping 20 matching lines @@
     operations.add('h.C.x');
     var tmp = xGetValue;
     xGetValue = null;
     return tmp;
   }
 
   static void set x(value) {
     operations.add('h.C.x=$value');
   }
 }