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

chromeos/components/tether/message_wrapper_unittest.cc

Index: chromeos/components/tether/message_wrapper_unittest.cc
diff --git a/chromeos/components/tether/message_wrapper_unittest.cc b/chromeos/components/tether/message_wrapper_unittest.cc
index 9e5ea88acf9329d423692da86e9c8dd446614258..78a7e248a301d126473987240db4e389b722f14f 100644
--- a/chromeos/components/tether/message_wrapper_unittest.cc
+++ b/chromeos/components/tether/message_wrapper_unittest.cc
@@ -103,6 +103,14 @@ TEST_F(MessageWrapperTest, TestToAndFromRawMessage_KeepAliveTickle) {
   VerifyProtoConversion(&tickle, wrapper, MessageType::KEEP_ALIVE_TICKLE);
 }
 
+TEST_F(MessageWrapperTest, TestToAndFromRawMessage_KeepAliveTickleResponse) {
+  KeepAliveTickleResponse response;
+
+  MessageWrapper wrapper(response);
+  VerifyProtoConversion(&response, wrapper,
+                        MessageType::KEEP_ALIVE_TICKLE_RESPONSE);
+}
+
 TEST_F(MessageWrapperTest, TestToAndFromRawMessage_TetherAvailabilityRequest) {
   TetherAvailabilityRequest request;