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

tests/language/optimized_setter_test.dart

Index: tests/language/optimized_setter_test.dart
diff --git a/tests/language/optimized_setter_test.dart b/tests/language/optimized_setter_test.dart
index e1c4f3d9aedf1b4f3025d1d6352e0a2551e16895..2c818776d5495f7b3489eab0a529fede72decc5e 100644
--- a/tests/language/optimized_setter_test.dart
+++ b/tests/language/optimized_setter_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 various setter situations, testing special cases in optimizing compiler.
-// VMOptions=--optimization-counter-threshold=10 --no-use-osr
+// VMOptions=--optimization-counter-threshold=10 --no-use-osr --no-background-compilation
 
 import "package:expect/expect.dart";