Make code compile with clang_use_chrome_plugin (part I)

core/fpdfapi/fpdf_page/include/cpdf_page.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_FPDFAPI_FPDF_PAGE_INCLUDE_CPDF_PAGE_H_
 #define CORE_FPDFAPI_FPDF_PAGE_INCLUDE_CPDF_PAGE_H_
 
 #include <memory>
 
 #include "core/fpdfapi/fpdf_page/include/cpdf_pageobjectholder.h"
 #include "core/fxcrt/include/fx_basic.h"
 #include "core/fxcrt/include/fx_coordinates.h"
 #include "core/fxcrt/include/fx_system.h"
 
 class CPDF_Dictionary;
 class CPDF_Document;
 class CPDF_Object;
 class CPDF_PageRenderCache;
 
 class CPDF_Page : public CPDF_PageObjectHolder {
  public:
   class View {};  // Caller implements as desired, empty here due to layering.
 
   CPDF_Page(CPDF_Document* pDocument,
             CPDF_Dictionary* pPageDict,
             bool bPageCache);
-  ~CPDF_Page();
+  ~CPDF_Page() override;
 
   void ParseContent();
 
   void GetDisplayMatrix(CFX_Matrix& matrix,
                         int xPos,
                         int yPos,
                         int xSize,
                         int ySize,
                         int iRotate) const;
 
@@ skipping 19 matching lines @@
 
   FX_FLOAT m_PageWidth;
   FX_FLOAT m_PageHeight;
   CFX_Matrix m_PageMatrix;
   View* m_pView;
   std::unique_ptr<CPDF_PageRenderCache> m_pPageRender;
   std::unique_ptr<CFX_Deletable> m_pRenderContext;
 };
 
 #endif  // CORE_FPDFAPI_FPDF_PAGE_INCLUDE_CPDF_PAGE_H_