Use override in more classes in core/

core/include/fpdfdoc/fpdf_ap.h

Index: core/include/fpdfdoc/fpdf_ap.h
diff --git a/core/include/fpdfdoc/fpdf_ap.h b/core/include/fpdfdoc/fpdf_ap.h
index 43452fdb47b8f655c2effdfe1fab0aadf41ac371..305834e96a31d5d3474f31e88d6e70faf902c300 100644
--- a/core/include/fpdfdoc/fpdf_ap.h
+++ b/core/include/fpdfdoc/fpdf_ap.h
@@ -51,20 +51,19 @@ struct CPVT_Color {
 class CPVT_Provider : public IPDF_VariableText_Provider {
  public:
   CPVT_Provider(IPVT_FontMap* pFontMap);
-
-  virtual ~CPVT_Provider();
-
-  int32_t GetCharWidth(int32_t nFontIndex, FX_WORD word, int32_t nWordStyle);
-
-  int32_t GetTypeAscent(int32_t nFontIndex);
-
-  int32_t GetTypeDescent(int32_t nFontIndex);
-
-  int32_t GetWordFontIndex(FX_WORD word, int32_t charset, int32_t nFontIndex);
-
-  FX_BOOL IsLatinWord(FX_WORD word);
-
-  int32_t GetDefaultFontIndex();
+  ~CPVT_Provider() override;
+
+  // IPDF_VariableText_Provider
+  int32_t GetCharWidth(int32_t nFontIndex,
+                       FX_WORD word,
+                       int32_t nWordStyle) override;
+  int32_t GetTypeAscent(int32_t nFontIndex) override;
+  int32_t GetTypeDescent(int32_t nFontIndex) override;
+  int32_t GetWordFontIndex(FX_WORD word,
+                           int32_t charset,
+                           int32_t nFontIndex) override;
+  FX_BOOL IsLatinWord(FX_WORD word) override;
+  int32_t GetDefaultFontIndex() override;
 
  private:
   IPVT_FontMap* m_pFontMap;