IPC: Introduce MessageAttachment and PlatformFileAttachment.

ipc/ipc.gypi

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'target_defaults': {
     'variables': {
       'ipc_target': 0,
     },
     'target_conditions': [
@@ skipping 18 matching lines @@
           'ipc_channel_win.h',
           'ipc_descriptors.h',
           'ipc_export.h',
           'ipc_forwarding_message_filter.cc',
           'ipc_forwarding_message_filter.h',
           'ipc_listener.h',
           'ipc_logging.cc',
           'ipc_logging.h',
           'ipc_message.cc',
           'ipc_message.h',
+          'ipc_message_attachment.cc',
+          'ipc_message_attachment.h',
           'ipc_message_attachment_set.cc',
           'ipc_message_attachment_set.h',
           'ipc_message_macros.h',
           'ipc_message_start.h',
           'ipc_message_utils.cc',
           'ipc_message_utils.h',
           'ipc_param_traits.h',
           'ipc_platform_file.cc',
           'ipc_platform_file.h',
+          'ipc_platform_file_attachment.cc',
+          'ipc_platform_file_attachment.h',
           'ipc_sender.h',
           'ipc_switches.cc',
           'ipc_switches.h',
           'ipc_sync_channel.cc',
           'ipc_sync_channel.h',
           'ipc_sync_message.cc',
           'ipc_sync_message.h',
           'ipc_sync_message_filter.cc',
           'ipc_sync_message_filter.h',
           'message_filter.cc',
@@ skipping 26 matching lines @@
           ['OS == "win" or OS == "ios"', {
             'sources!': [
               'unix_domain_socket_util.cc',
             ],
           }],
         ],
       }],
     ],
   },
 }