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

core/fpdfdoc/include/cpdf_variabletext.h

 // Copyright 2016 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 CORE_FPDFDOC_INCLUDE_CPDF_VARIABLETEXT_H_
 #define CORE_FPDFDOC_INCLUDE_CPDF_VARIABLETEXT_H_
 
 #include <memory>
@@ skipping 90 matching lines @@
   void SetFontSize(FX_FLOAT fFontSize) { m_fFontSize = fFontSize; }
   void SetCharArray(int32_t nCharArray) { m_nCharArray = nCharArray; }
   void SetAutoFontSize(FX_BOOL bAuto) { m_bAutoFontSize = bAuto; }
   void Initialize();
 
   FX_BOOL IsValid() const { return m_bInitial; }
 
   void RearrangeAll();
   void RearrangePart(const CPVT_WordRange& PlaceRange);
   void ResetAll();
-  void SetText(const FX_WCHAR* text);
+  void SetText(const CFX_WideString& text);
   CPVT_WordPlace InsertWord(const CPVT_WordPlace& place,
                             uint16_t word,
                             int32_t charset,
                             const CPVT_WordProps* pWordProps);
   CPVT_WordPlace InsertSection(const CPVT_WordPlace& place,
                                const CPVT_SecProps* pSecProps,
                                const CPVT_WordProps* pWordProps);
   CPVT_WordPlace InsertText(const CPVT_WordPlace& place, const FX_WCHAR* text);
   CPVT_WordPlace DeleteWords(const CPVT_WordRange& PlaceRange);
   CPVT_WordPlace DeleteWord(const CPVT_WordPlace& place);
@@ skipping 120 matching lines @@
   uint16_t m_wSubWord;
   FX_FLOAT m_fFontSize;
   FX_BOOL m_bInitial;
   CPDF_VariableText::Provider* m_pVTProvider;
   std::unique_ptr<CPDF_VariableText::Iterator> m_pVTIterator;
   CFX_FloatRect m_rcPlate;
   CPVT_FloatRect m_rcContent;
 };
 
 #endif  // CORE_FPDFDOC_INCLUDE_CPDF_VARIABLETEXT_H_