Fix windows build breakage at 25fa42f398d1

TBR=dsinclair@chromium.org

Review URL: https://codereview.chromium.org/2018563002 .
diff --git a/xfa/fgas/font/fgas_stdfontmgr.h b/xfa/fgas/font/fgas_stdfontmgr.h
index a455ee2..caa6626 100644
--- a/xfa/fgas/font/fgas_stdfontmgr.h
+++ b/xfa/fgas/font/fgas_stdfontmgr.h
@@ -51,8 +51,8 @@
                      uint32_t dwFontStyles,
                      uint16_t wCodePage = 0xFFFF) override;
 
-  void ClearFontCache();
-  void RemoveFont(IFX_Font* pFont);
+  void ClearFontCache() override;
+  void RemoveFont(IFX_Font* pFont) override;
 
  protected:
   void RemoveFont(CFX_MapPtrToPtr& fontMap, IFX_Font* pFont);