Update ChannelReader to use AttachmentBroker.

ipc/ipc_message.h

Index: ipc/ipc_message.h
diff --git a/ipc/ipc_message.h b/ipc/ipc_message.h
index 2d1e2ac6c37e9db1b04aa801d82f62ac2a054b9c..60e7ae89bf92304695c31695f868e4fbbc956038 100644
--- a/ipc/ipc_message.h
+++ b/ipc/ipc_message.h
@@ -19,6 +19,10 @@
 
 namespace IPC {
 
+namespace internal {
+class ChannelReader;
+}  // namespace internal
+
 //------------------------------------------------------------------------------
 
 struct LogData;
@@ -217,6 +221,7 @@ class IPC_EXPORT Message : public base::Pickle {
   friend class ChannelNacl;
   friend class ChannelPosix;
   friend class ChannelWin;
+  friend class internal::ChannelReader;
   friend class MessageReplyDeserializer;
   friend class SyncMessage;