Use annotations on confuse() functions

tests/language/const_map_test.dart

 // Copyright (c) 2014, 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.
 
 import "package:expect/expect.dart";
 
 /// Returns its argument.
 ///
 /// Prevents static optimizations and inlining.
-confuse(x) {
-  // DateTime.now() cannot be predicted statically.
-  if (new DateTime.now() == 42) return confuse(2);
-  return x;
-}
+@NoInline() @AssumeDynamic()
+confuse(x) => x;
 
 main() {
   // Make sure that const maps use the == operator and not identical. The
   // specification does not explicitly require it, but otherwise ints and
   // Strings wouldn't make much sense as keys.
   var m = const { 1: 42, "foo": 499 };
   Expect.equals(42, m[confuse(1.0)]);
   Expect.equals(499, m[confuse(new String.fromCharCodes("foo".runes))]);
 }