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

tests/language/call_closurization_test.dart

Index: tests/language/call_closurization_test.dart
diff --git a/tests/language/call_closurization_test.dart b/tests/language/call_closurization_test.dart
index 6c8dc71096c5cbca834c7b110cf245df0fec16f6..0d1733132743ad87d31b4567401e0e1d3c336841 100644
--- a/tests/language/call_closurization_test.dart
+++ b/tests/language/call_closurization_test.dart
@@ -1,7 +1,7 @@
 // Copyright (c) 2014, 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
 
 import "package:expect/expect.dart";