Fix issue 8218: "part of" directive comes after dartdoc comment.

pkg/unittest/lib/src/description.dart

Index: pkg/unittest/lib/src/description.dart
===================================================================
--- pkg/unittest/lib/src/description.dart	(revision 18082)
+++ pkg/unittest/lib/src/description.dart	(working copy)
@@ -1,14 +1,14 @@
 // 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.
+
+part of matcher;
+
 /**
  * The default implementation of IDescription. This should rarely need
  * substitution, although conceivably it is a place where other languages
  * could be supported.
  */
-
-part of matcher;
-
 class StringDescription implements Description {
   var _out;