Convert FWL_ERR into an enum class.

xfa/fxfa/app/xfa_fffield.h

Index: xfa/fxfa/app/xfa_fffield.h
diff --git a/xfa/fxfa/app/xfa_fffield.h b/xfa/fxfa/app/xfa_fffield.h
index 91908e3b98e9d5937f67cd7778af6ff51ba058fa..fd6661dea237f3ab3f70af3a4d74d395ce3ab268 100644
--- a/xfa/fxfa/app/xfa_fffield.h
+++ b/xfa/fxfa/app/xfa_fffield.h
@@ -85,10 +85,10 @@ class CXFA_FFField : public CXFA_FFWidget, public IFWL_WidgetDelegate {
   void SetEditScrollOffset();
 
  public:
-  virtual int32_t OnProcessMessage(CFWL_Message* pMessage);
-  virtual FWL_ERR OnProcessEvent(CFWL_Event* pEvent);
-  virtual FWL_ERR OnDrawWidget(CFX_Graphics* pGraphics,
-                               const CFX_Matrix* pMatrix = NULL);
+  virtual void OnProcessMessage(CFWL_Message* pMessage);
+  virtual void OnProcessEvent(CFWL_Event* pEvent);
+  virtual void OnDrawWidget(CFX_Graphics* pGraphics,
+                            const CFX_Matrix* pMatrix = NULL);
 
  protected:
   CFWL_Widget* m_pNormalWidget;