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

xfa/fxfa/fm2js/xfa_fm2jscontext.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/fxfa/fm2js/xfa_fm2jscontext.h"
 
 #include <time.h>
 
@@ skipping 4109 matching lines @@
   strEncode[8] = 0;
   CFX_WideTextBuf wsResultBuf;
   uint32_t ch = 0;
   int32_t iLen = wsHTMLString.GetLength();
   int32_t i = 0;
   const FX_WCHAR* pData = wsHTMLString.c_str();
   int32_t iIndex = 0;
   CFX_WideString htmlReserve;
   while (i < iLen) {
     ch = *(pData + i);
-    htmlReserve.Empty();
+    htmlReserve.clear();
     if (HTMLCode2STR(ch, htmlReserve)) {
       wsResultBuf.AppendChar(L'&');
       wsResultBuf << htmlReserve;
       wsResultBuf.AppendChar(L';');
     } else {
       if (ch >= 32 && ch <= 126) {
         wsResultBuf.AppendChar((FX_WCHAR)ch);
       } else if (ch < 256) {
         iIndex = ch / 16;
         strEncode[3] = strCode[iIndex];
@@ skipping 3089 matching lines @@
   CFX_WideString wsFormat;
   pAppProvider->LoadString(iStringID, wsFormat);
   CFX_WideString wsMessage;
   va_list arg_ptr;
   va_start(arg_ptr, iStringID);
   wsMessage.FormatV(wsFormat.c_str(), arg_ptr);
   va_end(arg_ptr);
   FXJSE_ThrowMessage(
       "", FX_UTF8Encode(wsMessage.c_str(), wsMessage.GetLength()).AsStringC());
 }