Update mirror tests for removed API.

tests/compiler/dart2js/message_kind_test.dart

 // Copyright (c) 2013, 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.
 
 import 'package:expect/expect.dart';
 import 'dart:async';
 import "package:async_helper/async_helper.dart";
 import '../../../sdk/lib/_internal/compiler/implementation/dart2jslib.dart' show
     DualKind,
     MessageKind;
 
 import 'message_kind_helper.dart';
 
 import 'dart:mirrors';
 
 main() {
   ClassMirror cls = reflectClass(MessageKind);
   Map<String, MessageKind> kinds = <String, MessageKind>{};
-  cls.variables.forEach((Symbol name, VariableMirror variable) {
+  cls.declarations.forEach((Symbol name, DeclarationMirror declaration) {
+    if (declaration is! VariableMirror) return;
+    VariableMirror variable = declaration;
     if (variable.isStatic) {
       var value = cls.getField(name).reflectee;
       if (value is MessageKind) {
         kinds[MirrorSystem.getName(name)] = value;
       } else if (value is DualKind) {
         kinds['${MirrorSystem.getName(name)}.error'] = value.error;
         kinds['${MirrorSystem.getName(name)}.warning'] = value.warning;
       } else {
         Expect.fail("Weird static field: '${MirrorSystem.getName(name)}'.");
       }
@@ skipping 20 matching lines @@
     Stopwatch sw = new Stopwatch()..start();
     return check(kinds[name], cachedCompiler).
         then((var compiler) {
           cachedCompiler = compiler;
           sw.stop();
           print("Checked '$name' in ${sw.elapsedMilliseconds}ms.");
         });
     }
   ));
 }