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

tests/language/vm/optimized_shl_test.dart

 
 // 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";
 
 // Test truncating left-shift that can deoptimize.
 // Regression test for issue 19330.
 
 test_shl(w, x) {
   x += 1;
   return w << x & 0xff ;
 }
 
 main() {
   for (var i = 0; i < 20; i++) test_shl(i, i % 10);
   Expect.equals(4, test_shl(1, 1));
 }