Convert FWL_ERR into an enum class.

xfa/fwl/theme/cfwl_formtp.h

Index: xfa/fwl/theme/cfwl_formtp.h
diff --git a/xfa/fwl/theme/cfwl_formtp.h b/xfa/fwl/theme/cfwl_formtp.h
index 24eaed8f85cd5978500b643424a091e1a36d2aa3..648dae4e0d8238f5b1cb5b2b674a2a687d430334 100644
--- a/xfa/fwl/theme/cfwl_formtp.h
+++ b/xfa/fwl/theme/cfwl_formtp.h
@@ -15,8 +15,8 @@ class CFWL_FormTP : public CFWL_WidgetTP {
   CFWL_FormTP();
   ~CFWL_FormTP() override;
 
-  FWL_ERR Initialize() override;
-  FWL_ERR Finalize() override;
+  FWL_Error Initialize() override;
+  FWL_Error Finalize() override;
   FX_BOOL IsValidWidget(IFWL_Widget* pWidget) override;
   uint32_t SetThemeID(IFWL_Widget* pWidget,
                       uint32_t dwThemeID,
@@ -25,7 +25,7 @@ class CFWL_FormTP : public CFWL_WidgetTP {
   FX_BOOL DrawText(CFWL_ThemeText* pParams) override;
   void* GetCapacity(CFWL_ThemePart* pThemePart,
                     CFWL_WidgetCapacity dwCapacity) override;
-  FWL_ERR GetPartRect(CFWL_ThemePart* pThemePart, CFX_RectF& rtPart) override;
+  FWL_Error GetPartRect(CFWL_ThemePart* pThemePart, CFX_RectF& rtPart) override;
 
  protected:
   void CalCloseBox(IFWL_Widget* pWidget, CFX_RectF& rect);