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

tests/language/instanceof_optimized_test.dart

Index: tests/language/instanceof_optimized_test.dart
diff --git a/tests/language/instanceof_optimized_test.dart b/tests/language/instanceof_optimized_test.dart
index e3f5965071620249b2dfb4ba927f30b892044543..820504f1b1fbfbf5fda52f13e6b62cc590a72aa3 100644
--- a/tests/language/instanceof_optimized_test.dart
+++ b/tests/language/instanceof_optimized_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.
 // Testing optimized 'is' tests.
-// VMOptions=--optimization-counter-threshold=5 --no-use-osr
+// VMOptions=--optimization-counter-threshold=5 --no-use-osr --no-background-compilation
 
 import "package:expect/expect.dart";