Add support for resolving symbolic links

pkg/analyzer/test/file_system/memory_file_system_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 analyzer.test.file_system.memory_file_system_test;
 
 import 'dart:async';
 import 'dart:core' hide Resource;
 
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 176 matching lines @@
     String newPath = '/foo/bar/baz';
     File file = provider.newFile(oldPath, 'text');
     provider.newFolder(newPath);
     expect(() {
       file.renameSync(newPath);
     }, throwsA(_isFileSystemException));
     expect(file.path, oldPath);
     expect(file.exists, isTrue);
   }
 
+  void test_resolveSymbolicLinksSync() {
+    File file = provider.newFile('/test.txt', 'text');
+    expect(file.resolveSymbolicLinksSync(), file);
+  }
+
   void test_shortName() {
     File file = provider.getResource('/foo/bar/file.txt');
     expect(file.shortName, 'file.txt');
   }
 
   void test_toString() {
     File file = provider.getResource('/foo/bar/file.txt');
     expect(file.toString(), '/foo/bar/file.txt');
   }
 
@@ skipping 519 matching lines @@
     return new Future.delayed(Duration.ZERO, computation);
   }
 
   _watchingFolder(String path, test(List<WatchEvent> changesReceived)) {
     Folder folder = provider.getResource(path);
     var changesReceived = <WatchEvent>[];
     folder.changes.listen(changesReceived.add);
     return test(changesReceived);
   }
 }