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

tests/language/div_with_power_of_two2_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 division by power of two.
 // Test that results before and after optimization are the same.
-// VMOptions=--optimization-counter-threshold=10 --no-use-osr
+// VMOptions=--optimization-counter-threshold=10 --no-use-osr --no-background-compilation
 
 import "package:expect/expect.dart";
 
 // [function, [list of tuples argument/result]].
 var expectedResults =
   [ [divBy1,
       [[134217730, 134217730],
        [-134217730, -134217730],
        [10, 10],
        [-10, -10]]],
@@ skipping 79 matching lines @@
         int arg = v[0];
         int res = v[1];
         Expect.equals(res, f(arg));
       }
     }
      Expect.throws(() => divBy0(4),
                   (e) => e is IntegerDivisionByZeroException
                          || e is UnsupportedError);
   }
 }