Add the ability to change the working directory

runtime/bin/directory.h

 // 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.
 
 #ifndef BIN_DIRECTORY_H_
 #define BIN_DIRECTORY_H_
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
 #include "bin/native_service.h"
@@ skipping 87 matching lines @@
     kListRequest = 4,
     kRenameRequest = 5
   };
 
   static bool List(const char* path,
                    bool recursive,
                    bool follow_links,
                    DirectoryListing* listing);
   static ExistsResult Exists(const char* path);
   static char* Current();
+  static bool SetCurrent(const char* path);
   static bool Create(const char* path);
   static char* CreateTemp(const char* const_template);
   static bool Delete(const char* path, bool recursive);
   static bool Rename(const char* path, const char* new_path);
   static Dart_Port GetServicePort();
 
  private:
   static NativeService directory_service_;
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(Directory);
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // BIN_DIRECTORY_H_