Update unittest to new package layout.

pkg/dartdoc/test/dartdoc_test.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.
 
 /// Unit tests for doc.
 #library('dartdoc_tests');
 
 // TODO(rnystrom): Use "package:" URL (#4968).
 #import('../lib/dartdoc.dart', prefix: 'dd');
 #import('../lib/markdown.dart', prefix: 'md');
-
-// TODO(rnystrom): Better path to unittest.
-#import('../../unittest/unittest.dart');
+#import('../../unittest/lib/unittest.dart');
 
 main() {
   group('countOccurrences', () {
     test('empty text returns 0', () {
       expect(dd.countOccurrences('', 'needle'), equals(0));
     });
 
     test('one occurrence', () {
       expect(dd.countOccurrences('bananarama', 'nara'), equals(1));
     });
@@ skipping 86 matching lines @@
           '../../other/sub/file.html'));
     });
 
     test('from nested to directory with different path', () {
       doc.startFile('dir/sub/file.html');
       expect(doc.relativePath('other/file.html'), equals(
           '../../other/file.html'));
     });
   });
 }