BREAKING CHANGE: enforce part of directive

tests/language/private1.dart

 // Copyright (c) 2012, 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.
 
 // Dart test for testing access to private fields.
 
+part of PrivateTest.dart; 
+
 main() {
   testPrivateTopLevel();
   testPrivateClasses();
 }
 
 void expectCatch(f) {
   bool threw = false;
   try {
     f();
   } catch (e) {
@@ skipping 71 matching lines @@
   Expect.equals(42, c.field2a());
   Expect.equals(99, LibOther3.c_field1b(c));
   Expect.equals(99, c.field1b());
   Expect.equals(1024, LibOther3.c_field2b(c));
   Expect.equals(1024, c.field2b());
   Expect.equals(499, c.field1c());
   Expect.equals(99, c.field1d());
   Expect.equals(499, _field1FromNewC4());
   Expect.equals(42, _field2FromNewC4());
 }