Use a pool of native ports for directory operations

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 "platform/globals.h"
+#include "platform/thread.h"
 
 class DirectoryListing {
  public:
   enum Response {
     kListDirectory = 0,
     kListFile = 1,
     kListError = 2,
     kListDone = 3
   };
 
@@ skipping 35 matching lines @@
 
   static bool Create(const char* path);
 
   static int CreateTemp(const char* const_template,
                         char** path,
                         char* os_error_message,
                         int os_error_message_len);
 
   static bool Delete(const char* path, bool recursive);
 
+  static Dart_Port GetServicePort();
+
+ private:
+  static dart::Mutex mutex_;
+  static int service_ports_size_;
+  static Dart_Port* service_ports_;
+  static int service_ports_index_;
+
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(Directory);
 };
 
 
 #endif  // BIN_DIRECTORY_H_