Runtime fixes on DDC tests

pkg/dev_compiler/test/codegen/language/string_optimizations_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.
 
 // Regression test for dart2js's type inferrer, that used to not
 // correclty infer optional named parameters.
 
 import "package:expect/expect.dart";
 import "compiler_annotations.dart";
 
 @DontInline()
 foo({path}) {
   () => 42;
   return path.toString();
 }
 
 @DontInline()
 bar({path}) {
   () => 42;
   return path;
 }
 
 main() {
-  var a = [foo(path: '42'), foo(), 42, bar(path: '54')];
+  var a = <Object>[foo(path: '42'), foo(), 42, bar(path: '54')];
   Expect.isTrue(a[1] is String);
   Expect.throws(() => bar().concat('54'), (e) => e is NoSuchMethodError);
 }