Create a desktop environment instance late so that it will see the curtain_required flag.

remoting/host/client_session.h

Index: remoting/host/client_session.h
diff --git a/remoting/host/client_session.h b/remoting/host/client_session.h
index f0d1e51083c6ca7bb6cbcbf70e2a975e2f2901bc..966a1f851f051ed6c72558a0efb5e8e589fcbbb8 100644
--- a/remoting/host/client_session.h
+++ b/remoting/host/client_session.h
@@ -81,8 +81,7 @@ class ClientSession
     virtual ~EventHandler() {}
   };
 
-  // |event_handler| must outlive |this|. |desktop_environment_factory| is only
-  // used by the constructor to create an instance of DesktopEnvironment.
+  // |event_handler| and |desktop_environment_factory| must outlive |this|.
   ClientSession(
       EventHandler* event_handler,
       scoped_refptr<base::SingleThreadTaskRunner> audio_task_runner,
@@ -162,8 +161,8 @@ class ClientSession
 
   std::string client_jid_;
 
-  // The desktop environment used by this session.
-  scoped_ptr<DesktopEnvironment> desktop_environment_;
+  // Used to create a DesktopEnvironment instance for this session.
+  DesktopEnvironmentFactory* desktop_environment_factory_;
 
   // Filter used as the final element in the input pipeline.
   protocol::InputFilter host_input_filter_;