[remoting android] Add and build host code.

remoting/host/me2me_desktop_environment.cc

Index: remoting/host/me2me_desktop_environment.cc
diff --git a/remoting/host/me2me_desktop_environment.cc b/remoting/host/me2me_desktop_environment.cc
index 35723dbc641e847722b93fa0a463ec821f0f9924..1395f9a4943a179d52b6f6f0d5ee79da9b8639e1 100644
--- a/remoting/host/me2me_desktop_environment.cc
+++ b/remoting/host/me2me_desktop_environment.cc
@@ -100,9 +100,9 @@ bool Me2MeDesktopEnvironment::InitializeSecurity(
   // running in the LoginWindow context, and refactor this into a separate
   // function to be used here and in CurtainMode::ActivateCurtain().
   bool want_user_interface = getuid() != 0;
-#elif defined(OS_WIN)
+#else
   bool want_user_interface = true;
-#endif  // defined(OS_WIN)
+#endif
 
   // Create the disconnect window.
   if (want_user_interface) {