Use override in more classes in fpdfsdk/

fpdfsdk/include/pdfwindow/PWL_SpecialButton.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_PDFWINDOW_PWL_SPECIALBUTTON_H_
 #define FPDFSDK_INCLUDE_PDFWINDOW_PWL_SPECIALBUTTON_H_
 
 #include "PWL_Button.h"
 
 class CPWL_PushButton : public CPWL_Button {
  public:
   CPWL_PushButton();
-  virtual ~CPWL_PushButton();
+  ~CPWL_PushButton() override;
 
-  virtual CFX_ByteString GetClassName() const;
-  virtual CPDF_Rect GetFocusRect() const;
+  // CPWL_Button
+  CFX_ByteString GetClassName() const override;
+  CPDF_Rect GetFocusRect() const override;
 };
 
 class CPWL_CheckBox : public CPWL_Button {
  public:
   CPWL_CheckBox();
-  virtual ~CPWL_CheckBox();
+  ~CPWL_CheckBox() override;
 
-  virtual CFX_ByteString GetClassName() const;
-  virtual FX_BOOL OnLButtonUp(const CPDF_Point& point, FX_DWORD nFlag);
-  virtual FX_BOOL OnChar(FX_WORD nChar, FX_DWORD nFlag);
+  // CPWL_Button
+  CFX_ByteString GetClassName() const override;
+  FX_BOOL OnLButtonUp(const CPDF_Point& point, FX_DWORD nFlag) override;
+  FX_BOOL OnChar(FX_WORD nChar, FX_DWORD nFlag) override;
 
   void SetCheck(FX_BOOL bCheck);
   FX_BOOL IsChecked() const;
 
  private:
   FX_BOOL m_bChecked;
 };
 
 class CPWL_RadioButton : public CPWL_Button {
  public:
   CPWL_RadioButton();
-  virtual ~CPWL_RadioButton();
+  ~CPWL_RadioButton() override;
 
-  virtual CFX_ByteString GetClassName() const;
-  virtual FX_BOOL OnLButtonUp(const CPDF_Point& point, FX_DWORD nFlag);
-  virtual FX_BOOL OnChar(FX_WORD nChar, FX_DWORD nFlag);
+  // CPWL_Button
+  CFX_ByteString GetClassName() const override;
+  FX_BOOL OnLButtonUp(const CPDF_Point& point, FX_DWORD nFlag) override;
+  FX_BOOL OnChar(FX_WORD nChar, FX_DWORD nFlag) override;
 
   void SetCheck(FX_BOOL bCheck);
   FX_BOOL IsChecked() const;
 
  private:
   FX_BOOL m_bChecked;
 };
 
 #endif  // FPDFSDK_INCLUDE_PDFWINDOW_PWL_SPECIALBUTTON_H_