Use override in more classes in core/

core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp

 // 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
 
 #include <utility>
 #include <vector>
 
 #include "../../../include/fpdfapi/fpdf_module.h"
@@ skipping 2797 matching lines @@
     buffer[offset++] = ch;
     if (offset == size) {
       break;
     }
   }
 }
 
 class CPDF_DataAvail final : public IPDF_DataAvail {
  public:
   CPDF_DataAvail(IFX_FileAvail* pFileAvail, IFX_FileRead* pFileRead);
-  ~CPDF_DataAvail();
+  ~CPDF_DataAvail() override;
 
   virtual FX_BOOL IsDocAvail(IFX_DownloadHints* pHints) override;
 
   virtual void SetDocument(CPDF_Document* pDoc) override;
 
   virtual FX_BOOL IsPageAvail(int iPage, IFX_DownloadHints* pHints) override;
 
   virtual int32_t IsFormAvail(IFX_DownloadHints* pHints) override;
 
   virtual int32_t IsLinearizedPDF() override;
@@ skipping 1884 matching lines @@
   return FALSE;
 }
 CPDF_PageNode::~CPDF_PageNode() {
   int32_t iSize = m_childNode.GetSize();
   for (int32_t i = 0; i < iSize; ++i) {
     CPDF_PageNode* pNode = (CPDF_PageNode*)m_childNode[i];
     delete pNode;
   }
   m_childNode.RemoveAll();
 }