Strong mode cleaning of many dart2js tests.

tests/compiler/dart2js/simple_inferrer_const_closure_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.
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
 import 'compiler_helper.dart';
 
 const String TEST = """
 
@@ skipping 24 matching lines @@
 
 void main() {
   Uri uri = new Uri(scheme: 'source');
   var compiler = compilerFor(TEST, uri);
   asyncTest(() => compiler.run(uri).then((_) {
         var typesInferrer = compiler.globalInference.typesInferrerInternal;
         var closedWorld = typesInferrer.closedWorld;
 
         checkReturn(String name, type) {
           var element = findElement(compiler, name);
-          Expect.equals(
-              type,
-              typesInferrer.getReturnTypeOfElement(element).simplify(compiler),
-              name);
+          dynamic returnType = typesInferrer.getReturnTypeOfElement(element);
+          Expect.equals(type, returnType.simplify(compiler), name);
         }
 
         checkReturn('method1', closedWorld.commonMasks.uint31Type);
         checkReturn('returnInt1', closedWorld.commonMasks.uint31Type);
 
         checkReturn('method2', closedWorld.commonMasks.uint31Type);
         checkReturn('returnInt2', closedWorld.commonMasks.uint31Type);
       }));
 }