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 290859ef3afb945470b7d9d6197bc2288e28dd4a..5faa00317cf7766e42b3b216317ef026f0ea2fc7 100644
--- a/remoting/host/chromoting_host.h
+++ b/remoting/host/chromoting_host.h
@@ -171,8 +171,6 @@ class ChromotingHost : public base::RefCountedThreadSafe<ChromotingHost>,
 
   int AuthenticatedClientsCount() const;
 
-  void EnableCurtainMode(bool enable);
-
   void StopScreenRecorder();
   void OnScreenRecorderStopped();
 
@@ -221,7 +219,6 @@ 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_;