Fix -Wnon-virtual-dtor compiler warnings.

core/src/fxcodec/jbig2/JBig2_Module.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 _JBIG2_MODULE_H_
 #define _JBIG2_MODULE_H_
 #include "JBig2_Define.h"
 class CJBig2_Module
 {
 public:
+    virtual ~CJBig2_Module() { }
 
     virtual void *JBig2_Malloc(FX_DWORD dwSize) = 0;
 
     virtual void *JBig2_Malloc2(FX_DWORD num, FX_DWORD dwSize) = 0;
 
     virtual void *JBig2_Malloc3(FX_DWORD num, FX_DWORD dwSize, FX_DWORD dwSize2) = 0;
 
     virtual void *JBig2_Realloc(FX_LPVOID pMem, FX_DWORD dwSize) = 0;
 
     virtual void JBig2_Free(FX_LPVOID pMem) = 0;
 
     virtual void JBig2_Assert(FX_INT32 nExpression) {};
 
     virtual     void JBig2_Error(FX_LPCSTR format, ...) {};
 
     virtual void JBig2_Warn(FX_LPCSTR format, ...) {};
 
     virtual void JBig2_Log(FX_LPCSTR format, ...) {};
 };
 #endif