Upgrade more confuse() functions

tests/compiler/dart2js_extra/mirrors_used_closure_test.dart

Index: tests/compiler/dart2js_extra/mirrors_used_closure_test.dart
diff --git a/tests/compiler/dart2js_extra/mirrors_used_closure_test.dart b/tests/compiler/dart2js_extra/mirrors_used_closure_test.dart
index 28c19a81be33c4a4251cf0a96f78928f5bc2968c..12551cfdf26165d1fe20e17da45f72a608d351cc 100644
--- a/tests/compiler/dart2js_extra/mirrors_used_closure_test.dart
+++ b/tests/compiler/dart2js_extra/mirrors_used_closure_test.dart
@@ -18,12 +18,9 @@ class B {
   bar() => 33;
 }
 
-// Uses DateTime.now to make it impossible to predict.
-// Uses recursive call to make it harder to inline.
-confuse(x) {
-  if (new DateTime.now().millisecondsSinceEpoch == 42) return confuse(x + 1);
-  return x;
-}
+@NoInline()
+@AssumeDynamic()
+confuse(x) => x;
 
 main() {
   var f = [new A(), new B()][confuse(0)].bar;