Refactor IT2Me-specific functions into a HostObserver subclass.

remoting/host/chromoting_host.h

Index: remoting/host/chromoting_host.h
diff --git a/remoting/host/chromoting_host.h b/remoting/host/chromoting_host.h
index c5651ccbd76c9b1c1fad79a17ac3a01723819888..b1394553a90c7c8d149be6d8f9688edcdb6127cd 100644
--- a/remoting/host/chromoting_host.h
+++ b/remoting/host/chromoting_host.h
@@ -172,8 +172,6 @@ class ChromotingHost : public base::RefCountedThreadSafe<ChromotingHost>,
 
   int AuthenticatedClientsCount() const;
 
-  void EnableCurtainMode(bool enable);
-
   void StopScreenRecorder();
   void OnScreenRecorderStopped();
 
@@ -222,7 +220,6 @@ class ChromotingHost : public base::RefCountedThreadSafe<ChromotingHost>,
 
   // TODO(sergeyu): The following members do not belong to
   // ChromotingHost and should be moved elsewhere.
-  bool is_curtained_;
   bool is_it2me_;
   std::string access_code_;
   UiStrings ui_strings_;