Stop converting widestring -> c_str -> widestring in several places.

fpdfsdk/pdfwindow/PWL_EditCtrl.h

 // 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
 
 #ifndef FPDFSDK_PDFWINDOW_PWL_EDITCTRL_H_
 #define FPDFSDK_PDFWINDOW_PWL_EDITCTRL_H_
 
 #include "core/fxcrt/include/fx_string.h"
@@ skipping 87 matching lines @@
   void IOnSetCaret(FX_BOOL bVisible,
                    const CFX_FloatPoint& ptHead,
                    const CFX_FloatPoint& ptFoot,
                    const CPVT_WordPlace& place);
   void IOnCaretChange(const CPVT_SecProps& secProps,
                       const CPVT_WordProps& wordProps);
   void IOnContentChange(const CFX_FloatRect& rcContent);
   void IOnInvalidateRect(CFX_FloatRect* pRect);
 
  protected:
-  void InsertText(const FX_WCHAR* csText);
-  void SetText(const FX_WCHAR* csText);
+  void InsertText(const CFX_WideString& wsText);
+  void SetText(const CFX_WideString& wsText);
   void CopyText();
   void PasteText();
   void CutText();
   void ShowVScrollBar(FX_BOOL bShow);
   void InsertWord(uint16_t word, int32_t nCharset);
   void InsertReturn();
 
   FX_BOOL IsWndHorV();
 
   void Delete();
@@ skipping 11 matching lines @@
   FX_BOOL m_bMouseDown;
 
  private:
   void CreateEditCaret(const PWL_CREATEPARAM& cp);
 
   int32_t m_nCharSet;
   int32_t m_nCodePage;
 };
 
 #endif  // FPDFSDK_PDFWINDOW_PWL_EDITCTRL_H_