Implement the full process interface for Windows

bin/process_impl.dart

 // Copyright (c) 2011, 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.
 
 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 104 matching lines @@
     }
     return false;
   }
 
   void _kill(int pid) native "Process_Kill";
 
   void close() {
     if (_closed) {
       throw new ProcessException("Process closed");
     }
-    _in.close();
-    _out.close();
-    _err.close();
-    _exitHandler.close();
+    if (_in._id != 0) { _in.close(); }
+    if (_out._id != 0) { _out.close(); }
+    if (_err._id != 0) { _err.close(); }
+    if (_exitHandler._id != 0) { _exitHandler.close(); }
     _closed = true;
   }
 
   void setExitHandler(void callback(int exitCode)) {
     if (_closed) {
       throw new ProcessException("Process closed");
     }
     if (_killed) {
       throw new ProcessException("Process killed");
     }
     _exitHandlerCallback = callback;
   }
 
   String _path;
   ObjectArray<String> _arguments;
   Socket _in;
   Socket _out;
   Socket _err;
   Socket _exitHandler;
   int _pid;
   bool _closed;
   bool _killed;
   bool _started;
   var _exitHandlerCallback;
 }