Use override in more classes in fpdfsdk/

fpdfsdk/include/fsdk_define.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_DEFINE_H_
 #define FPDFSDK_INCLUDE_FSDK_DEFINE_H_
 
 #include "../../core/include/fpdfapi/fpdf_module.h"
@@ skipping 28 matching lines @@
    ((FX_DWORD)rgb & 0x0000FF00) | (((FX_DWORD)rgb & 0x00FF0000) >> 16))
 #endif
 
 typedef unsigned int FX_UINT;
 class CRenderContext;
 class IFSDK_PAUSE_Adapter;
 
 class CPDF_CustomAccess final : public IFX_FileRead {
  public:
   CPDF_CustomAccess(FPDF_FILEACCESS* pFileAccess);
-  ~CPDF_CustomAccess() {}
+  ~CPDF_CustomAccess() override {}
 
-  virtual FX_FILESIZE GetSize() override { return m_FileAccess.m_FileLen; }
+  FX_FILESIZE GetSize() override { return m_FileAccess.m_FileLen; }
 
-  virtual void Release() override { delete this; }
+  void Release() override { delete this; }
 
-  virtual FX_BOOL ReadBlock(void* buffer,
-                            FX_FILESIZE offset,
-                            size_t size) override;
+  FX_BOOL ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) override;
 
  private:
   FPDF_FILEACCESS m_FileAccess;
 };
 
 void DropContext(void* data);
 void FSDK_SetSandBoxPolicy(FPDF_DWORD policy, FPDF_BOOL enable);
 FPDF_BOOL FSDK_IsSandBoxPolicyEnabled(FPDF_DWORD policy);
 void FPDF_RenderPage_Retail(CRenderContext* pContext,
                             FPDF_PAGE page,
                             int start_x,
                             int start_y,
                             int size_x,
                             int size_y,
                             int rotate,
                             int flags,
                             FX_BOOL bNeedToRestore,
                             IFSDK_PAUSE_Adapter* pause);
 
 #endif  // FPDFSDK_INCLUDE_FSDK_DEFINE_H_