Fix -Wnon-virtual-dtor compiler warnings.

core/include/fpdfdoc/fpdf_vt.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 _FPDF_VT_H_
 #define _FPDF_VT_H_
 #include "../fxcrt/fx_basic.h"
 #include "../fpdfapi/fpdf_parser.h"
@@ skipping 257 matching lines @@
 
     CPDF_Rect                                   rcSection;
 
     CPVT_SecProps                               SecProps;
 
     CPVT_WordProps                              WordProps;
 };
 class IPDF_VariableText_Provider
 {
 public:
+    virtual ~IPDF_VariableText_Provider() { }
 
     virtual FX_INT32                                            GetCharWidth(FX_INT32 nFontIndex, FX_WORD word, FX_INT32 nWordStyle) = 0;
 
     virtual FX_INT32                                            GetTypeAscent(FX_INT32 nFontIndex) = 0;
 
     virtual FX_INT32                                            GetTypeDescent(FX_INT32 nFontIndex) = 0;
 
     virtual FX_INT32                                            GetWordFontIndex(FX_WORD word, FX_INT32 charset, FX_INT32 nFontIndex) = 0;
 
     virtual FX_BOOL                                                     IsLatinWord(FX_WORD word) = 0;
 
     virtual FX_INT32                                            GetDefaultFontIndex() = 0;
 };
 class IPDF_VariableText_Iterator
 {
 public:
+    virtual ~IPDF_VariableText_Iterator() { }
 
     virtual FX_BOOL                                                     NextWord() = 0;
 
     virtual FX_BOOL                                                     PrevWord() = 0;
 
     virtual FX_BOOL                                                     NextLine() = 0;
 
     virtual FX_BOOL                                                     PrevLine() = 0;
 
     virtual FX_BOOL                                                     NextSection() = 0;
@@ skipping 12 matching lines @@
 
     virtual void                                                        SetAt(FX_INT32 nWordIndex) = 0;
 
     virtual void                                                        SetAt(const CPVT_WordPlace & place) = 0;
 
     virtual const CPVT_WordPlace &                      GetAt() const = 0;
 };
 class IPDF_VariableText
 {
 public:
-
     static IPDF_VariableText*                   NewVariableText();
 
     static void                                                 DelVariableText(IPDF_VariableText* pVT);
-public:
 
     virtual IPDF_VariableText_Provider*         SetProvider(IPDF_VariableText_Provider * pProvider) = 0;
 
     virtual IPDF_VariableText_Iterator*         GetIterator() = 0;
 
     virtual void                                                        SetPlateRect(const CPDF_Rect & rect) = 0;
 
     virtual void                                                        SetAlignment(FX_INT32 nFormat = 0) = 0;
 
     virtual void                                                        SetPasswordChar(FX_WORD wSubWord = '*') = 0;
@@ skipping 92 matching lines @@
 
     virtual CPVT_WordPlace                                      GetSectionEndPlace(const CPVT_WordPlace & place) const = 0;
 
     virtual void                                                        UpdateWordPlace(CPVT_WordPlace & place) const = 0;
 
     virtual CPVT_WordPlace                                      AjustLineHeader(const CPVT_WordPlace & place, FX_BOOL bPrevOrNext) const = 0;
 
     virtual FX_INT32                                            WordPlaceToWordIndex(const CPVT_WordPlace & place) const = 0;
 
     virtual CPVT_WordPlace                                      WordIndexToWordPlace(FX_INT32 index) const = 0;
+
+protected:
+    ~IPDF_VariableText() { }
 };
 #endif