[CrOS Tether] Add KeepAliveTickleResponse messages to both the proto file and MessageWrapper.

chromeos/components/tether/proto/tether.proto

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Definitions for tether API calls.
 
 syntax = "proto2";
 
 package chromeos.tether;
 
 option optimize_for = LITE_RUNTIME;
 
 // Types of messages which are sent between tether hosts and tether clients.
 enum MessageType {
   UNKNOWN_TYPE = 0;
   TETHER_AVAILABILITY_REQUEST = 1;
   TETHER_AVAILABILITY_RESPONSE = 2;
   CONNECT_TETHERING_REQUEST = 3;
   CONNECT_TETHERING_RESPONSE = 4;
   DISCONNECT_TETHERING_REQUEST = 5;
   KEEP_ALIVE_TICKLE = 6;
+  KEEP_ALIVE_TICKLE_RESPONSE = 7;
 }
 
 // Meant to communicate the host's current Wifi status. This is intended to
 // allow the client to warn the user that Tether will disconnect the host's
 // Wi-Fi, if applicable.
 // Next id: 3
 message WifiStatus {
   enum StatusCode {
     STATUS_UNKNOWN = 0;
     CONNECTED = 1;
@@ skipping 64 matching lines @@
 
   // Password for the new hotspot.
   optional string password = 3;
 
   optional DeviceStatus device_status = 4;
 }
 
 // Next id: 1
 message KeepAliveTickle {}
 
+// Next id: 2
+message KeepAliveTickleResponse {
+  optional DeviceStatus device_status = 1;
+}
+
 // Next id: 1
 message DisconnectTetheringRequest {}