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

tests/language/vm/uint32_shift_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';
 
 class Good {
   use(x) { return x & 0x1; }
 }
 
 class Bad {
   use(x) { return x & 0x100000000; }
 }
 
 f(o, x) => o.use(x << 1);
 
 main() {
   final good = new Good();
   final bad = new Bad();
   for (var i = 0; i < 20000; i++) {
     Expect.equals(0, f(good, 0x80000000));
   }
   Expect.equals(0x100000000, f(bad, 0x80000000));
 }