Use smart pointers for class owned pointers

fpdfsdk/include/fsdk_mgr.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_INCLUDE_FSDK_MGR_H_
 #define FPDFSDK_INCLUDE_FSDK_MGR_H_
 
 #include <map>
@@ skipping 601 matching lines @@
   void TakeOverPage() { m_bTakeOverPage = TRUE; }
 #endif  // PDF_ENABLE_XFA
 
  private:
   int GetPageIndexForStaticPDF() const;
 
   CFX_Matrix m_curMatrix;
   UnderlyingPageType* const m_page;
   std::unique_ptr<CPDF_AnnotList> m_pAnnotList;
   std::vector<CPDFSDK_Annot*> m_fxAnnotArray;
-  CPDFSDK_Document* m_pSDKDoc;
+  CPDFSDK_Document* const m_pSDKDoc;
 #ifdef PDF_ENABLE_XFA
   CPDFSDK_Annot* m_CaptureWidget;
 #else  // PDF_ENABLE_XFA
   CPDFSDK_Widget* m_CaptureWidget;
   FX_BOOL m_bTakeOverPage;
 #endif  // PDF_ENABLE_XFA
   FX_BOOL m_bEnterWidget;
   FX_BOOL m_bExitWidget;
   FX_BOOL m_bOnWidget;
   FX_BOOL m_bValid;
   FX_BOOL m_bLocked;
 };
 
 #endif  // FPDFSDK_INCLUDE_FSDK_MGR_H_