Really remove io support when dart:io is unsupported.

runtime/bin/filter.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/filter.h"
+
 #include "bin/dartutils.h"
-#include "bin/filter.h"
 #include "bin/io_buffer.h"
 
 #include "include/dart_api.h"
 
 namespace dart {
 namespace bin {
 
 const int kZLibFlagUseGZipHeader = 16;
 const int kZLibFlagAcceptAnyHeader = 32;
 
@@ skipping 441 matching lines @@
   }
 
   delete[] current_buffer_;
   current_buffer_ = NULL;
   // Either 0 Byte processed or error
   return error ? -1 : 0;
 }
 
 }  // namespace bin
 }  // namespace dart
+
+#endif  // !defined(DART_IO_DISABLED)