Minor work for background compilation

tests/standalone/assert_assignable_canon_test.dart

 // Copyright (c) 2016, 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=--enable-inlining-annotations --optimization-counter-threshold=10
+// VMOptions=--enable-inlining-annotations --optimization-counter-threshold=10 --no-background-compilation
 
 const AlwaysInline = "AlwaysInline";
 const NeverInline = "NeverInline";
 
 abstract class A<T extends A<T>> {
   @AlwaysInline
   f(x) => new R<T>(x);
 }
 
 class B extends A<B> {}
@@ skipping 12 matching lines @@
 // function (Instance::IsInstanceOf does not work for TypeRefs).
 @NeverInline
 f(o) => new B().f(o);
 
 main() {
   final o = new D();
   for (var i = 0; i < 10; i++) {
     f(o);
   }
 }