Pass u2f message callback vector as a const reference

device/u2f/u2f_register.h

 // 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.
 
 #ifndef DEVICE_U2F_U2F_REGISTER_H_
 #define DEVICE_U2F_U2F_REGISTER_H_
 
 #include <vector>
 
 #include "u2f_request.h"
 
 namespace device {
 
 class U2fRegister : public U2fRequest {
  public:
   U2fRegister(const std::vector<uint8_t>& challenge_hash,
               const std::vector<uint8_t>& app_param,
               const ResponseCallback& cb);
   ~U2fRegister() override;
 
   static std::unique_ptr<U2fRequest> TryRegistration(
       const std::vector<uint8_t>& challenge_hash,
       const std::vector<uint8_t>& app_param,
       const ResponseCallback& cb);
 
  private:
   void TryDevice() override;
-  void OnTryDevice(U2fReturnCode, std::vector<uint8_t>);
+  void OnTryDevice(U2fReturnCode return_code,
+                   const std::vector<uint8_t>& response_data);
 
   std::vector<uint8_t> challenge_hash_;
   std::vector<uint8_t> app_param_;
   base::WeakPtrFactory<U2fRegister> weak_factory_;
 };
 
 }  // namespace device
 
 #endif  // DEVICE_U2F_U2F_REGISTER_H_