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

tests/language/vm/load_to_load_forwarding_vm_test.dart

 // Copyright (c) 2012, 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 correctness of side effects tracking used by load to load forwarding.
 
-// VMOptions=--optimization-counter-threshold=10
+// VMOptions=--optimization-counter-threshold=10 --no-background-compilation
 
 import "package:expect/expect.dart";
 import "dart:typed_data";
 
 class A {
   var x, y;
   A(this.x, this.y);
 }
 
 foo(a) {
@@ skipping 570 matching lines @@
     Expect.equals(43, testAliasingStoreIndexed(global_array));
   }
 
   for (var i = 0; i < 20; i++) {
     Expect.equals(2.0, testViewAliasing1());
     Expect.equals(2.0, testViewAliasing2());
     Expect.equals(2.0, testViewAliasing3());
     Expect.equals(2.0, testViewAliasing4());
   }
 }