Use override in more classes in fpdfsdk/

fpdfsdk/include/pdfwindow/PWL_SpecialButton.h

Index: fpdfsdk/include/pdfwindow/PWL_SpecialButton.h
diff --git a/fpdfsdk/include/pdfwindow/PWL_SpecialButton.h b/fpdfsdk/include/pdfwindow/PWL_SpecialButton.h
index 8cfe819a67340c9f27c3ea9c8f20211a51649c06..a62d18d257b9190e8eac05720cd1b6bc7d53ea50 100644
--- a/fpdfsdk/include/pdfwindow/PWL_SpecialButton.h
+++ b/fpdfsdk/include/pdfwindow/PWL_SpecialButton.h
@@ -12,20 +12,22 @@
 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;
@@ -37,11 +39,12 @@ class CPWL_CheckBox : public CPWL_Button {
 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;