[dart:io] Remove DART_IO_DISABLED

runtime/bin/process.cc

Index: runtime/bin/process.cc
diff --git a/runtime/bin/process.cc b/runtime/bin/process.cc
index 6ecdbca16515e9a0160d6652c8c673492cdb83b2..290174964cd625da412f0c24ffade38192de9ded 100644
--- a/runtime/bin/process.cc
+++ b/runtime/bin/process.cc
@@ -2,8 +2,6 @@
 // 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"
@@ -378,5 +376,3 @@ void Process::GetRSSInformation(int64_t* max_rss, int64_t* current_rss) {
 
 }  // namespace bin
 }  // namespace dart
-
-#endif  // !defined(DART_IO_DISABLED)