Use native wrapper fields to store socket ids.

runtime/bin/process_impl.dart

 // 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.
 
 _exit(int status) native "Exit";
 
 class _ProcessStartStatus {
   int _errorCode;  // Set to OS error code if process start failed.
   String _errorMessage;  // Set to OS error message if process start failed.
 }
@@ skipping 131 matching lines @@
                                 _exitHandler,
                                 status);
     if (!success) {
       close();
       _reportError(new ProcessException(status._errorMessage,
                                         status._errorCode));
       return;
     }
     _started = true;
 
+    _in._closed = false;
+    _out._closed = false;
+    _err._closed = false;
+    _exitHandler._closed = false;
+
     // Make sure to activate socket handlers now that the file
     // descriptors have been set.
     _in._activateHandlers();
     _out._activateHandlers();
     _err._activateHandlers();
 
     // Setup an exit handler to handle internal cleanup and possible
     // callback when a process terminates.
     int exitDataRead = 0;
     final int EXIT_DATA_SIZE = 8;
@@ skipping 224 matching lines @@
 
 class _ProcessResult implements ProcessResult {
   const _ProcessResult(int this.exitCode,
                        String this.stdout,
                        String this.stderr);
 
   final int exitCode;
   final String stdout;
   final String stderr;
 }