Really remove io support when dart:io is unsupported.

runtime/bin/dartutils.h

 // 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.
 
 #ifndef BIN_DARTUTILS_H_
 #define BIN_DARTUTILS_H_
 
+#include "bin/isolate_data.h"
 #include "include/dart_api.h"
 #include "include/dart_native_api.h"
-
 #include "platform/assert.h"
 #include "platform/globals.h"
 
-#include "bin/isolate_data.h"
-
 namespace dart {
 namespace bin {
 
 // Forward declarations.
 class File;
 class OSError;
 
 /* Handles error handles returned from Dart API functions.  If a value
  * is an error, uses Dart_PropagateError to throw it to the enclosing
  * Dart activation.  Otherwise, returns the original handle.
@@ skipping 575 matching lines @@
 
   ~ScopedBlockingCall() {
     Dart_ThreadEnableProfiling();
   }
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // BIN_DARTUTILS_H_