face: face refactoring completion

* delete old Face
* rename LpFace as Face
* eliminate LpFaceWrapper and use new Face

refs #3172

Change-Id: I08c3a5dfb4cc1b9834b30cccd9ab634535d0608c
diff --git a/daemon/face/channel.hpp b/daemon/face/channel.hpp
index cb5ed27..640395a 100644
--- a/daemon/face/channel.hpp
+++ b/daemon/face/channel.hpp
@@ -26,12 +26,10 @@
 #ifndef NFD_DAEMON_FACE_CHANNEL_HPP
 #define NFD_DAEMON_FACE_CHANNEL_HPP
 
-#include "common.hpp"
+#include "face.hpp"
 
 namespace nfd {
 
-class Face;
-
 /**
  * \brief Prototype for the callback that is invoked when the face
  *        is created (as a response to incoming connection or after
@@ -69,6 +67,16 @@
   return m_uri;
 }
 
+/** \brief invokes a callback when the face is closed
+ *  \param face the face
+ *  \param f the callback to be invoked when the face enters CLOSED state
+ *
+ *  This function connects a callback to the afterStateChange signal on the \p face,
+ *  and invokes \p f when the state becomes CLOSED.
+ */
+void
+connectFaceClosedSignal(Face& face, const std::function<void()>& f);
+
 } // namespace nfd
 
 #endif // NFD_DAEMON_FACE_CHANNEL_HPP