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

tests/language/constant_string_interpolation_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.
-// 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() {
   final a = new A();
   for (int i = 0; i < 20; i++) {
     final r = interpolIt(a);
     Expect.stringEquals("hello home", r);
   }
   final b = new B();
   // Deoptimize "interpolIt".
   final r = interpolIt(b);
   Expect.stringEquals("hello world", r);
 }
 
 
 String interpolIt(v) {
   // String interpolation will be constant folded.
   return "hello ${v.foo()}";
 }
 
 class A {
   foo() => "home";
 }
 
 class B {
   foo() => "world";
 }