Convert FWL_ERR into an enum class.

xfa/fwl/basewidget/ifwl_spinbutton.h

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef XFA_FWL_BASEWIDGET_IFWL_SPINBUTTON_H_
 #define XFA_FWL_BASEWIDGET_IFWL_SPINBUTTON_H_
 
 #include "xfa/fwl/core/fwl_widgetimp.h"
 
 #define FWL_CLASS_SpinButton L"FWL_SPINBUTTON"
 #define FWL_CLASSHASH_SpinButton 3793043646
 #define FWL_STYLEEXE_SPB_Vert (1L << 0)
 
 BEGIN_FWL_EVENT_DEF(CFWL_EvtSpbClick, CFWL_EventType::Click)
 FX_BOOL m_bUp;
 END_FWL_EVENT_DEF
 
 class IFWL_SpinButton : public IFWL_Widget {
  public:
   static IFWL_SpinButton* Create(const CFWL_WidgetImpProperties& properties,
                                  IFWL_Widget* pOuter);
 
-  FWL_ERR EnableButton(FX_BOOL bEnable, FX_BOOL bUp = TRUE);
+  FWL_Error EnableButton(FX_BOOL bEnable, FX_BOOL bUp = TRUE);
   FX_BOOL IsButtonEnable(FX_BOOL bUp = TRUE);
 
  protected:
   IFWL_SpinButton();
 };
 
 #endif  // XFA_FWL_BASEWIDGET_IFWL_SPINBUTTON_H_