Remove some c_str() calls from StringCs in xfa docs.

xfa/fxfa/app/xfa_fftextedit.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/app/xfa_fftextedit.h"
 
 #include <vector>
 
@@ skipping 176 matching lines @@
   ValidateNumberField(wsText);
   return FALSE;
 }
 void CXFA_FFTextEdit::ValidateNumberField(const CFX_WideString& wsText) {
   CXFA_WidgetAcc* pAcc = GetDataAcc();
   if (pAcc && pAcc->GetUIType() == XFA_ELEMENT_NumericEdit) {
     IXFA_AppProvider* pAppProvider = GetApp()->GetAppProvider();
     if (pAppProvider) {
       CFX_WideString wsTitle;
       pAppProvider->LoadString(XFA_IDS_AppName, wsTitle);
-      CFX_WideString wsMessage;
       CFX_WideString wsError;
       pAppProvider->LoadString(XFA_IDS_ValidateNumberError, wsError);
       CFX_WideString wsSomField;
       pAcc->GetNode()->GetSOMExpression(wsSomField);
+      CFX_WideString wsMessage;
       wsMessage.Format(wsError.c_str(), wsText.c_str(), wsSomField.c_str());
-      pAppProvider->MsgBox(wsMessage.AsStringC(), wsTitle.AsStringC(),
-                           XFA_MBICON_Error, XFA_MB_OK);
+      pAppProvider->MsgBox(wsMessage, wsTitle, XFA_MBICON_Error, XFA_MB_OK);
     }
   }
 }
 FX_BOOL CXFA_FFTextEdit::IsDataChanged() {
   return (m_dwStatus & XFA_WIDGETSTATUS_TextEditValueChanged) != 0;
 }
 uint32_t CXFA_FFTextEdit::GetAlignment() {
   uint32_t dwExtendedStyle = 0;
   if (CXFA_Para para = m_pDataAcc->GetPara()) {
     int32_t iHorz = para.GetHorizontalAlign();
@@ skipping 578 matching lines @@
 
 void CXFA_FFDateTimeEdit::OnProcessEvent(CFWL_Event* pEvent) {
   if (pEvent->GetClassID() == CFWL_EventType::SelectChanged) {
     CFWL_Event_DtpSelectChanged* event = (CFWL_Event_DtpSelectChanged*)pEvent;
     OnSelectChanged(m_pNormalWidget->GetWidget(), event->iYear, event->iMonth,
                     event->iDay);
     return;
   }
   CXFA_FFTextEdit::OnProcessEvent(pEvent);
 }