Fix names of some tests in dart2js_extra.

tests/compiler/dart2js_extra/22776_test.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.
 
 // Regression test for http://dartbug.com/22776/
 
 import "package:expect/expect.dart";
 
 class A {}
 
 main() {
   try {
     print(id(new Duration(milliseconds: 10)));
     print(id(3) ~/ new A());
   } catch (e) {
     print("Error '$e' ${e.runtimeType}");
   }
 }
 
 @AssumeDynamic()
 @NoInline()
 id(x) => x;