Add --no-background-compilation to tests that expect to run code in optimized form

tests/language/nan_identical_test.dart

Index: tests/language/nan_identical_test.dart
diff --git a/tests/language/nan_identical_test.dart b/tests/language/nan_identical_test.dart
index a567f8021b94f4e1ca135ad11dbb7cc8b7a4b84c..5f171be5c4c6ba6893663414bd65f82cbeb0239b 100644
--- a/tests/language/nan_identical_test.dart
+++ b/tests/language/nan_identical_test.dart
@@ -2,7 +2,7 @@
 // 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.
 // Test a new statement by itself.
-// VMOptions=--optimization-counter-threshold=4
+// VMOptions=--optimization-counter-threshold=4 --no-background-compilation
 
 import 'dart:typed_data';