Use annotations on confuse() in null_test

tests/language/null_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.
 // Second dart test program.
 
 // VMOptions=--optimization-counter-threshold=5
 
 import "dart:mirrors";
 import "package:expect/expect.dart";
 
@@ skipping 18 matching lines @@
 
 class Generic2<T, S> {
   bool test(o) => new Generic<T>().test(o);
   T cast(o) => new Generic<T>().cast(o);
   Type get type => new Generic<T>().type;
 }
 
 // Magic incantation to avoid the compiler recognizing the constant values
 // at compile time. If the result is computed at compile time, the dynamic code
 // will not be tested.
-confuse(x) {
-  try {
-    if (new DateTime.now().millisecondsSinceEpoch == 42) x = 42;
-    throw [x];
-  } on dynamic catch (e) { return e[0]; }
-  return 42;
-}
+@NoInline()
+@AssumeDynamic()
+confuse(x) => x;
 
 void main() {
   for (int i = 0; i < 10; i++) {
     test();
   }
 }
 
 void test() {
   new BadInherit();  // Make sure class is referenced.
 
@@ skipping 142 matching lines @@
   var capture = new CaptureInvocationMirror();
   var mirror = capture.notDeclared();
   Expect.throws(() => noSuchMethod(mirror));
   Expect.throws(() => Function.apply(noSuchMethod, [mirror]));
 }
 
 
 class CaptureInvocationMirror {
   noSuchMethod(mirror) => mirror;
 }