Cleanup IFWL_Widget visibility and virtual parameters

xfa/fwl/core/ifwl_listbox.h

Index: xfa/fwl/core/ifwl_listbox.h
diff --git a/xfa/fwl/core/ifwl_listbox.h b/xfa/fwl/core/ifwl_listbox.h
index 943c064afee783cb06133b768e8cd3bb4473241e..fed3337a9912cce055d082cdd23330768db4a37b 100644
--- a/xfa/fwl/core/ifwl_listbox.h
+++ b/xfa/fwl/core/ifwl_listbox.h
@@ -107,12 +107,12 @@ class IFWL_ListBox : public IFWL_Widget {
 
   // IFWL_Widget
   FWL_Type GetClassID() const override;
-  FWL_Error GetWidgetRect(CFX_RectF& rect, bool bAutoSize = false) override;
-  FWL_Error Update() override;
+  void GetWidgetRect(CFX_RectF& rect, bool bAutoSize = false) override;
+  void Update() override;
   FWL_WidgetHit HitTest(FX_FLOAT fx, FX_FLOAT fy) override;
-  FWL_Error DrawWidget(CFX_Graphics* pGraphics,
-                       const CFX_Matrix* pMatrix = nullptr) override;
-  FWL_Error SetThemeProvider(IFWL_ThemeProvider* pThemeProvider) override;
+  void DrawWidget(CFX_Graphics* pGraphics,
+                  const CFX_Matrix* pMatrix = nullptr) override;
+  void SetThemeProvider(IFWL_ThemeProvider* pThemeProvider) override;
   void OnProcessMessage(CFWL_Message* pMessage) override;
   void OnProcessEvent(CFWL_Event* pEvent) override;
   void OnDrawWidget(CFX_Graphics* pGraphics,