Don't compile io_service if io is not supported.

runtime/bin/io_impl_sources.gypi

 # 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.
 
 # This file contains some C++ sources for the dart:io library.  The other
 # implementation files are in builtin_impl_sources.gypi.
 {
   'sources': [
     'crypto.cc',
     'crypto_android.cc',
     'crypto_linux.cc',
     'crypto_macos.cc',
     'crypto_win.cc',
     'eventhandler.cc',
     'eventhandler.h',
     'eventhandler_android.cc',
     'eventhandler_linux.cc',
     'eventhandler_linux.h',
     'eventhandler_macos.cc',
     'eventhandler_macos.h',
     'eventhandler_win.cc',
     'eventhandler_win.h',
     'filter.cc',
     'filter.h',
     'filter_unsupported.cc',
     'io_service.cc',
     'io_service.h',
+    'io_service_unsupported.cc',
     'net/nss_memio.cc',
     'net/nss_memio.h',
     'platform.cc',
     'platform.h',
     'platform_android.cc',
     'platform_linux.cc',
     'platform_macos.cc',
     'platform_win.cc',
     'process.cc',
     'process.h',
@@ skipping 14 matching lines @@
     'stdin.h',
     'stdin_android.cc',
     'stdin_linux.cc',
     'stdin_macos.cc',
     'stdin_win.cc',
   ],
   'conditions': [
     ['dart_io_support==1', {
       'sources!' : [
         'filter_unsupported.cc',
         'secure_socket_unsupported.cc',

[Bill Hesse, 2013/09/25 16:25:54]

Add io_service_unsupported.cc here.

But the problem may be that when the dartium snapshot is built, this has been
compiled, but File and Directory (used by snapshot_gen) will call it probably.

[Anders Johnsen, 2013/09/25 16:29:02]

Done.

       ],
     },{  # else dart_io_support == 0
       'sources!' : [
         'filter.cc',
         'filter.h',
+        'io_service.cc',
+        'io_service.h',
         'net/nss_memio.cc',
         'net/nss_memio.h',
         'secure_socket.cc',
         'secure_socket.h',
       ],
     }],
   ],
 }