Incremental compilation: correctly track emitted constants.

dart/tests/try/web/incremental_compilation_update_test.dart

 // Copyright (c) 2014, 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 trydart.incremental_compilation_update_test;
 
 import 'dart:html' hide
     Element;
 
 import 'dart:async' show
@@ skipping 1684 matching lines @@
   const B(this.value);
 
   toString() => 'B($value)';
 }
 
 main() {
   print(const B(const A('v2')));
   print(const A(const B('v2')));
 }
 """,
-            // TODO(ahe): Broken test, wrong output.
-            const <String>['B(null)', 'A(null)']),
-/* These are the correct expectations:
             const <String>['B(A(v2))', 'A(B(v2))']),
-*/
     ],
 
     // Test constants of new classes.
     const <ProgramResult>[
         const ProgramResult(
             r"""
 class A {
   final value;
   const A(this.value);
 
@@ skipping 224 matching lines @@
   position: absolute;
   left: 0px;
   width: 3em;
   text-align: right;
   background-color: lightgoldenrodyellow;
 }
 ''');
   style.type = 'text/css';
   return style;
 }