Extract constants into separate libarary.

pkg/analysis_server/test/resource_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 test.resource;
 
 import 'dart:async';
-import 'dart:io' as io;
 
 import 'mocks.dart';
 
 import 'package:analysis_server/src/resource.dart';
 import 'package:analyzer/src/generated/engine.dart' show TimestampedData;
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:path/path.dart';
 import 'package:unittest/unittest.dart';
 import 'package:watcher/watcher.dart';
 
@@ skipping 403 matching lines @@
           expect(relative.fullName, '/foo/bar/baz.dart');
         });
       });
     });
   });
 }
 
 var _isFile = new isInstanceOf<File>();
 var _isFolder = new isInstanceOf<Folder>();
 var _isMemoryResourceException = new isInstanceOf<MemoryResourceException>();