Really remove io support when dart:io is unsupported.

runtime/bin/socket.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/socket.h"
+
 #include "bin/dartutils.h"
 #include "bin/io_buffer.h"
 #include "bin/isolate_data.h"
 #include "bin/lockers.h"
-#include "bin/socket.h"
 #include "bin/thread.h"
 #include "bin/utils.h"
 
+#include "include/dart_api.h"
+
 #include "platform/globals.h"
 #include "platform/utils.h"
 
-#include "include/dart_api.h"
-
 namespace dart {
 namespace bin {
 
 static const int kSocketIdNativeField = 0;
 
 
 ListeningSocketRegistry *globalTcpListeningSocketRegistry = NULL;
 
 
 void ListeningSocketRegistry::Initialize() {
@@ skipping 839 matching lines @@
   Dart_Handle err =
       Dart_GetNativeInstanceField(socket_obj, kSocketIdNativeField, &socket);
   if (Dart_IsError(err)) {
     Dart_PropagateError(err);
   }
   return socket;
 }
 
 }  // namespace bin
 }  // namespace dart
+
+#endif  // !defined(DART_IO_DISABLED)