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

tests/language/many_generic_instanceof_test.dart

 // 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";
 part "generic_instanceof.dart";
 
 class ManyGenericInstanceofTest {
   static testMain() {
     for (int i = 0; i < 20; i++) {
       GenericInstanceof.testMain();
     }
   }
 }
 
 main() {
   ManyGenericInstanceofTest.testMain();
 }