Reuse WeakFactory from U2fDevice derived classes

device/u2f/u2f_hid_device.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_HID_DEVICE_H_
 #define DEVICE_U2F_U2F_HID_DEVICE_H_
 
 #include <list>
 
 #include "base/cancelable_callback.h"
@@ skipping 72 matching lines @@
                           bool success,
                           scoped_refptr<net::IOBuffer> buf,
                           size_t size);
   void OnWink(const WinkCallback& callback,
               bool success,
               std::unique_ptr<U2fMessage> response);
   void ArmTimeout(const DeviceCallback& callback);
   void OnTimeout(const DeviceCallback& callback);
   void OnDeviceTransact(bool success,
                         std::unique_ptr<U2fApduResponse> response);
+  base::WeakPtr<U2fDevice> GetWeakPtr() override;
 
   State state_;
   base::CancelableClosure timeout_callback_;
   std::list<std::pair<std::unique_ptr<U2fApduCommand>, DeviceCallback>>
       pending_transactions_;
   scoped_refptr<HidDeviceInfo> device_info_;
   scoped_refptr<HidConnection> connection_;
   base::WeakPtrFactory<U2fHidDevice> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(U2fHidDevice);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_U2F_U2F_HID_DEVICE_H_