Runtime fixes on DDC tests

pkg/dev_compiler/test/codegen/language/string_optimizations_test.dart

Index: pkg/dev_compiler/test/codegen/language/string_optimizations_test.dart
diff --git a/pkg/dev_compiler/test/codegen/language/string_optimizations_test.dart b/pkg/dev_compiler/test/codegen/language/string_optimizations_test.dart
index 1374bb3760dc29759d69ac3dd4f3e7767616cd20..afaf7ea01b062cb39597ccffdd91aca2c336778f 100644
--- a/pkg/dev_compiler/test/codegen/language/string_optimizations_test.dart
+++ b/pkg/dev_compiler/test/codegen/language/string_optimizations_test.dart
@@ -21,7 +21,7 @@ bar({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);
 }