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

tests/language/vm/if_conversion_vm_test.dart

 // Copyright (c) 2013, 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.
 
 // Test if-convertion pass in the optimizing compiler.
-// VMOptions=--optimization-counter-threshold=10 --no-use-osr
+// VMOptions=--optimization-counter-threshold=10 --no-use-osr --no-background-compilation
 
 import "package:expect/expect.dart";
 
 f1(i) => (i == 0) ? 0 : 1;
 f2(i) => (i == 0) ? 2 : 3;
 f3(i) => (i == null) ? 0 : 1;
 f4(i) => (i == null) ? 2 : 3;
 
 f5(i) => (i != 0) ? 0 : 1;
 f6(i) => (i != 0) ? 2 : 3;
@@ skipping 126 matching lines @@
 
   Expect.equals(0, f24(0));
   Expect.equals(1, f24(-1));
 
   Expect.equals(0, f25(-1));
   Expect.equals(1, f25(0));
 
   Expect.equals(0, f26(0));
   Expect.equals(1, f26(1));
 }