face: deduplicate callback typedefs between Channel and ProtocolFactory

This should have been part of commit 1d7e7afd381b91b6194d516826294b7f41f78745

Change-Id: I61623152180d4df288fc7dd3c225518e438d2bda
Refs: #3258
diff --git a/daemon/face/protocol-factory.hpp b/daemon/face/protocol-factory.hpp
index e2491ef..31efe8b 100644
--- a/daemon/face/protocol-factory.hpp
+++ b/daemon/face/protocol-factory.hpp
@@ -26,27 +26,10 @@
 #ifndef NFD_DAEMON_FACE_PROTOCOL_FACTORY_HPP
 #define NFD_DAEMON_FACE_PROTOCOL_FACTORY_HPP
 
-#include "common.hpp"
+#include "channel.hpp"
 
 namespace nfd {
 
-class Channel;
-class Face;
-
-/**
- * \brief Prototype for the callback that is invoked when the face
- *        is created (as a response to incoming connection or after
- *        connection is established)
- */
-typedef function<void(const shared_ptr<Face>& newFace)> FaceCreatedCallback;
-
-/**
- * \brief Prototype for the callback that is invoked when the face
- *        fails to be created
- */
-typedef function<void(const std::string& reason)> FaceCreationFailedCallback;
-
-
 /**
  * \brief Abstract base class for all protocol factories
  */