[dart:io] Remove DART_IO_DISABLED

runtime/bin/process.cc

 // Copyright (c) 2013, 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.
 
-#if !defined(DART_IO_DISABLED)
-
 #include "bin/process.h"
 
 #include "bin/dartutils.h"
 #include "bin/io_buffer.h"
 #include "bin/log.h"
 #include "bin/platform.h"
 #include "bin/socket.h"
 #include "bin/utils.h"
 
 #include "include/dart_api.h"
@@ skipping 354 matching lines @@
 
 void Process::GetRSSInformation(int64_t* max_rss, int64_t* current_rss) {
   ASSERT(max_rss != NULL);
   ASSERT(current_rss != NULL);
   *max_rss = Process::MaxRSS();
   *current_rss = Process::CurrentRSS();
 }
 
 }  // namespace bin
 }  // namespace dart
-
-#endif  // !defined(DART_IO_DISABLED)