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

tests/lib/math/double_pow_test.dart

 // Copyright (c) 2011, 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=5
+// VMOptions=--optimization-counter-threshold=5 --no-background-compilation
 
 library math_test;
 import "package:expect/expect.dart";
 import 'dart:math';
 
 void checkVeryClose(double a, double b) {
   // We find a ulp (unit in the last place) by shifting the original number
   // to the right. This only works if we are not too close to infinity or if
   // we work with denormals.
   // We special case for 0.0, but not for infinity.
@@ skipping 138 matching lines @@
   // Conversion to double.
 
   // The second argument is an odd integer as int, but not when converted
   // to double.
   Expect.identical(Infinity, pow(-0.0, -9223372036854775809));
 }
 
 main() {
   for (int i = 0; i < 10; i++) test();
 }