Revert "Switch libraries to using new tags."

sdk/lib/io/process.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.
 
-part of dart.io;
-
 // TODO(ager): The only reason for this class is that we
 // cannot patch a top-level at this point.
 class _ProcessUtils {
   external static _exit(int status);
 }
 
 /** Exit the Dart VM process with the given [status] code. */
 void exit(int status) {
   if (status is !int) {
     throw new ArgumentError("int status expected");
@@ skipping 222 matching lines @@
   /**
    * Contains the system message for the process exception if any.
    */
   final String message;
 
   /**
    * Contains the OS error code for the process exception if any.
    */
   final int errorCode;
 }