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 74bd74157bedb06f82e4f7150333727eea775238..878784718dd5c969ce0cebfb3f69bac6b4a18d06 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;