Cleanup remaining IFWL files for visiblity and usage.

xfa/fwl/core/cfwl_checkbox.h

Index: xfa/fwl/core/cfwl_checkbox.h
diff --git a/xfa/fwl/core/cfwl_checkbox.h b/xfa/fwl/core/cfwl_checkbox.h
index 730b906ba4a586b4c33a7716a3073d0b51f0b201..fb7a9ae1bf9ed06fffdfd414f2646f85065fbf80 100644
--- a/xfa/fwl/core/cfwl_checkbox.h
+++ b/xfa/fwl/core/cfwl_checkbox.h
@@ -17,17 +17,14 @@ class CFWL_CheckBox : public CFWL_Widget, public IFWL_CheckBoxDP {
 
   void Initialize();
 
-  FWL_Error SetCaption(const CFX_WideStringC& wsCaption);
-  FWL_Error SetBoxSize(FX_FLOAT fHeight);
-  int32_t GetCheckState();
-  FWL_Error SetCheckState(int32_t iCheck);
-
   // IFWL_DataProvider
   void GetCaption(IFWL_Widget* pWidget, CFX_WideString& wsCaption) override;
 
   // IFWL_CheckBoxDP
   FX_FLOAT GetBoxSize(IFWL_Widget* pWidget) override;
 
+  void SetBoxSize(FX_FLOAT fHeight);
+
  private:
   FX_FLOAT m_fBoxHeight;
   CFX_WideString m_wsCaption;