Reuse WeakFactory from U2fDevice derived classes

device/u2f/u2f_device.cc

Index: device/u2f/u2f_device.cc
diff --git a/device/u2f/u2f_device.cc b/device/u2f/u2f_device.cc
index 1b2f2b7089403ece0ff1e221d78922f45be760aa..2545cc12f819ca8b51b9c5a40439cf3fc2ac389d 100644
--- a/device/u2f/u2f_device.cc
+++ b/device/u2f/u2f_device.cc
@@ -10,8 +10,7 @@
 
 namespace device {
 
-U2fDevice::U2fDevice()
-    : channel_id_(kBroadcastChannel), capabilities_(0), weak_factory_(this) {}
+U2fDevice::U2fDevice() : channel_id_(kBroadcastChannel), capabilities_(0) {}
 
 U2fDevice::~U2fDevice() {}
 
@@ -24,9 +23,9 @@ void U2fDevice::Register(const std::vector<uint8_t>& app_param,
     callback.Run(U2fReturnCode::INVALID_PARAMS, std::vector<uint8_t>());
     return;
   }
-  DeviceTransact(std::move(register_cmd),
-                 base::Bind(&U2fDevice::OnRegisterComplete,
-                            weak_factory_.GetWeakPtr(), callback));
+  DeviceTransact(
+      std::move(register_cmd),
+      base::Bind(&U2fDevice::OnRegisterComplete, GetWeakPtr(), callback));
 }
 
 void U2fDevice::Sign(const std::vector<uint8_t>& app_param,
@@ -39,9 +38,8 @@ void U2fDevice::Sign(const std::vector<uint8_t>& app_param,
     callback.Run(U2fReturnCode::INVALID_PARAMS, std::vector<uint8_t>());
     return;
   }
-  DeviceTransact(std::move(sign_cmd),
-                 base::Bind(&U2fDevice::OnSignComplete,
-                            weak_factory_.GetWeakPtr(), callback));
+  DeviceTransact(std::move(sign_cmd), base::Bind(&U2fDevice::OnSignComplete,
+                                                 GetWeakPtr(), callback));
 }
 
 void U2fDevice::Version(const VersionCallback& callback) {
@@ -50,9 +48,9 @@ void U2fDevice::Version(const VersionCallback& callback) {
     callback.Run(false, ProtocolVersion::UNKNOWN);
     return;
   }
-  DeviceTransact(std::move(version_cmd),
-                 base::Bind(&U2fDevice::OnVersionComplete,
-                            weak_factory_.GetWeakPtr(), callback));
+  DeviceTransact(
+      std::move(version_cmd),
+      base::Bind(&U2fDevice::OnVersionComplete, GetWeakPtr(), callback));
 }
 
 void U2fDevice::OnRegisterComplete(