Reuse WeakFactory from U2fDevice derived classes

device/u2f/u2f_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_DEVICE_H_
 #define DEVICE_U2F_U2F_DEVICE_H_
 
 #include <vector>
 
 #include "base/callback.h"
@@ skipping 42 matching lines @@
   static constexpr uint8_t kWinkCapability = 0x01;
   static constexpr uint8_t kLockCapability = 0x02;
   static constexpr uint32_t kBroadcastChannel = 0xffffffff;
 
   U2fDevice();
 
   // Pure virtual function defined by each device type, implementing
   // the device communication transaction.
   virtual void DeviceTransact(std::unique_ptr<U2fApduCommand> command,
                               const DeviceCallback& callback) = 0;
+  virtual base::WeakPtr<U2fDevice> GetWeakPtr() = 0;
 
   uint32_t channel_id_;
   uint8_t capabilities_;
 
  private:
   void OnRegisterComplete(const MessageCallback& callback,
                           bool success,
                           std::unique_ptr<U2fApduResponse> register_response);
   void OnSignComplete(const MessageCallback& callback,
                       bool success,
                       std::unique_ptr<U2fApduResponse> sign_response);
   void OnVersionComplete(const VersionCallback& callback,
                          bool success,
                          std::unique_ptr<U2fApduResponse> version_response);
   void OnLegacyVersionComplete(
       const VersionCallback& callback,
       bool success,
       std::unique_ptr<U2fApduResponse> legacy_version_response);
   void OnWink(const WinkCallback& callback,
               bool success,
               std::unique_ptr<U2fApduResponse> response);
 
-  base::WeakPtrFactory<U2fDevice> weak_factory_;
-
   DISALLOW_COPY_AND_ASSIGN(U2fDevice);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_U2F_U2F_DEVICE_H_