Update ChannelReader to use AttachmentBroker.

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': [
       # This part is shared between the targets defined below.
       ['ipc_target==1', {
         'sources': [
+          'attachment_broker.cc',
           'attachment_broker.h',
           'attachment_broker_messages.h',
           'attachment_broker_win.cc',
           'attachment_broker_win.h',
           'brokerable_attachment.cc',
           'brokerable_attachment.h',
           'handle_attachment_win.cc',
           'handle_attachment_win.h',
           'ipc_channel.cc',
           'ipc_channel.h',
@@ skipping 76 matching lines @@
           ['OS == "win" or OS == "ios"', {
             'sources!': [
               'unix_domain_socket_util.cc',
             ],
           }],
         ],
       }],
     ],
   },
 }