Provide access to stdin, stdout and stderr

runtime/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 11 matching lines @@
     int len = arguments.length;
     _arguments = new ObjectArray<String>(len);
     for (int i = 0; i < len; i++) {
       var arg = arguments[i];
       if (arg is !String) {
         throw new ProcessException("Non-string argument: $arg");
       }
       _arguments[i] = arguments[i];
     }
 
-    _in = new _Socket._internalOutputOnly();
-    _out = new _Socket._internalInputOnly();
-    _err = new _Socket._internalOutputOnly();
+    _in = new _Socket._internalReadOnly();  // stdout coming from process.
+    _out = new _Socket._internalWriteOnly();  // stdin going to process.
+    _err = new _Socket._internalReadOnly();  // stderr coming from process.
     _exitHandler = new _Socket._internal();
     _closed = false;
     _killed = false;
     _started = false;
     _exitHandlerCallback = null;
   }
 
   int _intFromBytes(List<int> bytes, int offset) {
     return (bytes[offset] +
             (bytes[offset + 1] << 8) +
@@ skipping 126 matching lines @@
   Socket _in;
   Socket _out;
   Socket _err;
   Socket _exitHandler;
   int _pid;
   bool _closed;
   bool _killed;
   bool _started;
   var _exitHandlerCallback;
 }