Convert FWL_ERR into an enum class.

xfa/fxfa/app/xfa_fwladapter.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_FXFA_APP_XFA_FWLADAPTER_H_
 #define XFA_FXFA_APP_XFA_FWLADAPTER_H_
 
 #include "core/fxcrt/include/fx_coordinates.h"
 #include "core/fxcrt/include/fx_system.h"
 #include "xfa/fwl/core/fwl_error.h"
 
 class IFWL_Widget;
 
 class CXFA_FWLAdapterWidgetMgr {
  public:
   CXFA_FWLAdapterWidgetMgr();
   ~CXFA_FWLAdapterWidgetMgr();
 
-  FWL_ERR RepaintWidget(IFWL_Widget* pWidget, const CFX_RectF* pRect);
+  FWL_Error RepaintWidget(IFWL_Widget* pWidget, const CFX_RectF* pRect);
   FX_BOOL GetPopupPos(IFWL_Widget* pWidget,
                       FX_FLOAT fMinHeight,
                       FX_FLOAT fMaxHeight,
                       const CFX_RectF& rtAnchor,
                       CFX_RectF& rtPopup);
 };
 
 #endif  // XFA_FXFA_APP_XFA_FWLADAPTER_H_