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

tests/language/many_generic_instanceof_test.dart

Index: tests/language/many_generic_instanceof_test.dart
diff --git a/tests/language/many_generic_instanceof_test.dart b/tests/language/many_generic_instanceof_test.dart
index a37e84e47db10585f96f2b9f3b4d9bfdb5b30304..ffaccd7b3a0b328acd260452ecc195481fdc0a20 100644
--- a/tests/language/many_generic_instanceof_test.dart
+++ b/tests/language/many_generic_instanceof_test.dart
@@ -1,7 +1,7 @@
 // Copyright (c) 2011, 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.
-// VMOptions=--optimization-counter-threshold=10
+// VMOptions=--optimization-counter-threshold=10 --no-background-compilation
 
 library GenericInstanceofTest.dart;
 import "package:expect/expect.dart";