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

tests/language/truncdiv_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.
 // Dart test optimization of modulo operator on Smi.
-// VMOptions=--optimization-counter-threshold=10 --no-use-osr
+// VMOptions=--optimization-counter-threshold=10 --no-use-osr --no-background-compilation
 
 import "package:expect/expect.dart";
 
 
 main() {
   for (int i = -30; i < 30; i++) {
     Expect.equals(i % 9, foo(i, 9));
     // Zero test is done outside the loop.
     if (i < 0) {
       Expect.equals(i ~/ -i, foo2(i));
     } else if (i > 0) {
       Expect.equals(i ~/ i, foo2(i));
     }
   }
   Expect.throws(() => foo(12, 0), (e) => e is IntegerDivisionByZeroException);
   Expect.throws(() => foo2(0), (e) => e is IntegerDivisionByZeroException);
 }
 
 foo(i, x) => i % x;
 
 foo2(i) {
-  // Make sure x has a range computed. 
+  // Make sure x has a range computed.
   var x = 0;
   if (i < 0) {
     x = -i;
   } else {
     x = i;
   }
   return i ~/ x;
 }