Strong mode cleaning of many dart2js tests.

tests/compiler/dart2js/simple_inferrer_closure_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 "package:async_helper/async_helper.dart";
 import 'compiler_helper.dart';
 import 'type_mask_test_helper.dart';
 
 const String TEST = """
@@ skipping 128 matching lines @@
 
         checkReturn(
             'returnDyn1', closedWorld.commonMasks.dynamicType.nonNullable());
         checkReturn(
             'returnDyn2', closedWorld.commonMasks.dynamicType.nonNullable());
         checkReturn(
             'returnDyn3', closedWorld.commonMasks.dynamicType.nonNullable());
         checkReturn('returnNum1', closedWorld.commonMasks.numType);
 
         checkReturnInClass(String className, String methodName, type) {
-          var cls = findElement(compiler, className);
+          dynamic cls = findElement(compiler, className);
           var element = cls.lookupLocalMember(methodName);
           Expect.equals(
               type,
               simplify(
                   typesInferrer.getReturnTypeOfElement(element), closedWorld));
         }
 
-        var cls = findElement(compiler, 'A');
+        dynamic cls = findElement(compiler, 'A');
         checkReturnInClass(
             'A', 'foo', new TypeMask.nonNullExact(cls, closedWorld));
       }));
 }