Use virtual function to retrieve interface pointer

xfa/fwl/lightwidget/cfwl_checkbox.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "xfa/fwl/lightwidget/cfwl_checkbox.h"
 
 #include <memory>
 
 #include "xfa/fwl/core/fwl_error.h"
 
+IFWL_CheckBox* CFWL_CheckBox::GetWidget() {
+  return static_cast<IFWL_CheckBox*>(m_pIface.get());
+}
+
+const IFWL_CheckBox* CFWL_CheckBox::GetWidget() const {
+  return static_cast<IFWL_CheckBox*>(m_pIface.get());
+}
+
 CFWL_CheckBox* CFWL_CheckBox::Create() {
   return new CFWL_CheckBox;
 }
 
 FWL_Error CFWL_CheckBox::Initialize(const CFWL_WidgetProperties* pProperties) {
   if (m_pIface)
     return FWL_Error::Indefinite;
   if (pProperties) {
     *m_pProperties = *pProperties;
   }
   std::unique_ptr<IFWL_CheckBox> pCheckBox(IFWL_CheckBox::Create(
       m_pProperties->MakeWidgetImpProperties(&m_checkboxData), nullptr));
   FWL_Error ret = pCheckBox->Initialize();
   if (ret != FWL_Error::Succeeded) {
     return ret;
   }
-  m_pIface = pCheckBox.release();
+  m_pIface = std::move(pCheckBox);
   CFWL_Widget::Initialize();
   return FWL_Error::Succeeded;
 }
 
 FWL_Error CFWL_CheckBox::SetCaption(const CFX_WideStringC& wsCaption) {
   m_checkboxData.m_wsCaption = wsCaption;
   return FWL_Error::Succeeded;
 }
 
 FWL_Error CFWL_CheckBox::SetBoxSize(FX_FLOAT fHeight) {
   m_checkboxData.m_fBoxHeight = fHeight;
   return FWL_Error::Succeeded;
 }
 
 int32_t CFWL_CheckBox::GetCheckState() {
-  return static_cast<IFWL_CheckBox*>(m_pIface)->GetCheckState();
+  return GetWidget()->GetCheckState();
 }
 
 FWL_Error CFWL_CheckBox::SetCheckState(int32_t iCheck) {
-  return static_cast<IFWL_CheckBox*>(m_pIface)->SetCheckState(iCheck);
+  return GetWidget()->SetCheckState(iCheck);
 }
 
 CFWL_CheckBox::CFWL_CheckBox() {}
 
 CFWL_CheckBox::~CFWL_CheckBox() {}
 
 CFWL_CheckBox::CFWL_CheckBoxDP::CFWL_CheckBoxDP()
     : m_fBoxHeight(16.0f), m_wsCaption(L"Check box") {}
 
 FWL_Error CFWL_CheckBox::CFWL_CheckBoxDP::GetCaption(
     IFWL_Widget* pWidget,
     CFX_WideString& wsCaption) {
   wsCaption = m_wsCaption;
   return FWL_Error::Succeeded;
 }
 
 FX_FLOAT CFWL_CheckBox::CFWL_CheckBoxDP::GetBoxSize(IFWL_Widget* pWidget) {
   return m_fBoxHeight;
 }