Handle pairing_client_id in the negotiating authenticators.

remoting/protocol/negotiating_client_authenticator.h

Index: remoting/protocol/negotiating_client_authenticator.h
diff --git a/remoting/protocol/negotiating_client_authenticator.h b/remoting/protocol/negotiating_client_authenticator.h
index 855e64a3a63eb58868d2e1775d0dacdab96df349..9688dcde02988c24b861a5ffa7a26570296d9e4c 100644
--- a/remoting/protocol/negotiating_client_authenticator.h
+++ b/remoting/protocol/negotiating_client_authenticator.h
@@ -60,6 +60,8 @@ class NegotiatingClientAuthenticator : public NegotiatingAuthenticatorBase {
                                        const base::Closure& resume_callback,
                                        const std::string& shared_secret);
 
+  bool is_paired();
+
   std::string local_id_;
   std::string remote_id_;