change to source-order crawling of directives instead of alphabetical

test/parts/bar.dart

 // Copyright (c) 2015, 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.
-@initializeTracker
-library initialize.test.foo;
-
-import 'package:initialize/src/initialize_tracker.dart';
+part of initialize.initializer_parts_test;
 
 @initializeTracker
-class Foo {}
+class Bar2 {}
 
 @initializeTracker
-fooBar() {}
+class Bar {}
 
 @initializeTracker
-foo() {}
+bar2() {}
+
+@initializeTracker
+bar() {}