Replace calls to deprecated CFX_{Wide,Byte}String::Empty()

xfa/fwl/core/fwl_targetimp.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/core/fwl_targetimp.h"
 
 FWL_ERR IFWL_Target::GetClassName(CFX_WideString& wsClass) const {
   return m_pImpl->GetClassName(wsClass);
 }
 uint32_t IFWL_Target::GetClassID() const {
   return m_pImpl->GetClassID();
 }
 FX_BOOL IFWL_Target::IsInstance(const CFX_WideStringC& wsClass) const {
   return m_pImpl->IsInstance(wsClass);
 }
 FWL_ERR IFWL_Target::Initialize() {
   return m_pImpl->Initialize();
 }
 FWL_ERR IFWL_Target::Finalize() {
   return m_pImpl->Finalize();
 }
 IFWL_Target::~IFWL_Target() {
   delete m_pImpl;
 }
 CFWL_TargetImp::CFWL_TargetImp() {}
 CFWL_TargetImp::~CFWL_TargetImp() {}
 FWL_ERR CFWL_TargetImp::GetClassName(CFX_WideString& wsClass) const {
-  wsClass.Empty();
+  wsClass.clear();
   return FWL_ERR_Succeeded;
 }
 uint32_t CFWL_TargetImp::GetClassID() const {
   return 0;
 }
 FX_BOOL CFWL_TargetImp::IsInstance(const CFX_WideStringC& wsClass) const {
   return FALSE;
 }
 FWL_ERR CFWL_TargetImp::Initialize() {
   return FWL_ERR_Succeeded;
 }
 FWL_ERR CFWL_TargetImp::Finalize() {
   return FWL_ERR_Succeeded;
 }