pkg/docgen: moved model classes into minilibs

pkg/docgen/test/single_library_test.dart

 // Copyright (c) 2014, 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.
 
 library single_library_test;
 
 import 'dart:io';
 
 import 'package:path/path.dart' as path;
 import 'package:unittest/unittest.dart';
 
+import '../lib/src/exports/mirrors_util.dart' as dart2js_util;
 import '../lib/docgen.dart';
-import '../../../sdk/lib/_internal/compiler/implementation/mirrors/mirrors_util.dart'
-    as dart2js_util;
 
 const String DART_LIBRARY = '''
   library test;
   /**
    * Doc comment for class [A].
    *
    * Multiline Test
    */
   /*
    * Normal comment for class A.
@@ skipping 98 matching lines @@
               'doThis').children.first.text;
           expect(methodDocComment, 'test.A.doThis');
 
           // Testing something with no reference
           var libraryDocComment = method.fixReference('foobar').text;
           expect(libraryDocComment, 'foobar');
         }).whenComplete(() => temporaryDir.deleteSync(recursive: true));
     });
   });
 }