Use override in more classes in fpdfsdk/

fpdfsdk/include/pdfwindow/PWL_Caret.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_CARET_H_
 #define FPDFSDK_INCLUDE_PDFWINDOW_PWL_CARET_H_
 
 #include "PWL_Wnd.h"
 
 struct PWL_CARET_INFO {
  public:
   PWL_CARET_INFO() : bVisible(FALSE), ptHead(0, 0), ptFoot(0, 0) {}
 
   FX_BOOL bVisible;
   CPDF_Point ptHead;
   CPDF_Point ptFoot;
 };
 
 class CPWL_Caret : public CPWL_Wnd {
  public:
   CPWL_Caret();
-  virtual ~CPWL_Caret();
+  ~CPWL_Caret() override;
 
-  virtual CFX_ByteString GetClassName() const;
-  virtual void GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream);
-  virtual void DrawThisAppearance(CFX_RenderDevice* pDevice,
-                                  CPDF_Matrix* pUser2Device);
-  virtual void InvalidateRect(CPDF_Rect* pRect = NULL);
-  virtual void SetVisible(FX_BOOL bVisible) {}
-  virtual void TimerProc();
+  // CPWL_Wnd
+  CFX_ByteString GetClassName() const override;
+  void GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) override;
+  void DrawThisAppearance(CFX_RenderDevice* pDevice,
+                          CPDF_Matrix* pUser2Device) override;
+  void InvalidateRect(CPDF_Rect* pRect = NULL) override;
+  void SetVisible(FX_BOOL bVisible) override {}
+  void TimerProc() override;
+
   void SetCaret(FX_BOOL bVisible,
                 const CPDF_Point& ptHead,
                 const CPDF_Point& ptFoot);
   CFX_ByteString GetCaretAppearanceStream(const CPDF_Point& ptOffset);
   void SetInvalidRect(CPDF_Rect rc) { m_rcInvalid = rc; }
 
  private:
   void GetCaretApp(CFX_ByteTextBuf& sAppStream, const CPDF_Point& ptOffset);
   CPDF_Rect GetCaretRect() const;
 
   FX_BOOL m_bFlash;
   CPDF_Point m_ptHead;
   CPDF_Point m_ptFoot;
   FX_FLOAT m_fWidth;
   int32_t m_nDelay;
   CPDF_Rect m_rcInvalid;
 };
 
 #endif  // FPDFSDK_INCLUDE_PDFWINDOW_PWL_CARET_H_