[dart:io] Remove DART_IO_DISABLED

runtime/bin/platform.cc

 // 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.
 
-#if !defined(DART_IO_DISABLED)
-
 #include "bin/platform.h"
 
 #include "bin/file.h"
 #include "bin/utils.h"
 #include "include/dart_api.h"
 
 namespace dart {
 namespace bin {
 
 void FUNCTION_NAME(Platform_NumberOfProcessors)(Dart_NativeArguments args) {
@@ skipping 88 matching lines @@
   const char* locale = Platform::LocaleName();
   if (locale == NULL) {
     Dart_SetReturnValue(args, DartUtils::NewDartOSError());
   } else {
     Dart_SetReturnValue(args, Dart_NewStringFromCString(locale));
   }
 }
 
 }  // namespace bin
 }  // namespace dart
-
-#endif  // !defined(DART_IO_DISABLED)