Fix private_test to reflect new, better warning.

tests/compiler/dart2js/private_test.dart

Index: tests/compiler/dart2js/private_test.dart
diff --git a/tests/compiler/dart2js/private_test.dart b/tests/compiler/dart2js/private_test.dart
index f36513ec1a75c1f7c299609a5a01509cf2f0491d..df4c40ac57e1af210d95b4d6b2577a88279d7495 100644
--- a/tests/compiler/dart2js/private_test.dart
+++ b/tests/compiler/dart2js/private_test.dart
@@ -131,7 +131,7 @@ void main() {
   analyze('publicClass = new PublicClass.publicConstructor();');
   // Call private constructor on public class.
   analyze('publicClass = new PublicClass._privateConstructor();',
-      MessageKind.CANNOT_FIND_CONSTRUCTOR);
+      MessageKind.PRIVATE_ACCESS);
   // Read from private field on public class.
   analyze('var value = publicClass._privateField;',
       MessageKind.PRIVATE_ACCESS);