Convert FWL_ERR into an enum class.

xfa/fwl/theme/cfwl_pushbuttontp.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_THEME_CFWL_PUSHBUTTONTP_H_
 #define XFA_FWL_THEME_CFWL_PUSHBUTTONTP_H_
 
 #include "xfa/fwl/theme/cfwl_widgettp.h"
 
 class CFWL_PushButtonTP : public CFWL_WidgetTP {
  public:
   CFWL_PushButtonTP();
   ~CFWL_PushButtonTP() override;
 
   FX_BOOL IsValidWidget(IFWL_Widget* pWidget) override;
   uint32_t SetThemeID(IFWL_Widget* pWidget,
                       uint32_t dwThemeID,
                       FX_BOOL bChildren = TRUE) override;
   FX_BOOL DrawBackground(CFWL_ThemeBackground* pParams) override;
   void* GetCapacity(CFWL_ThemePart* pThemePart,
                     CFWL_WidgetCapacity dwCapacity) override;
-  FWL_ERR Initialize() override;
-  FWL_ERR Finalize() override;
+  FWL_Error Initialize() override;
+  FWL_Error Finalize() override;
 
  protected:
   struct PBThemeData {
     FX_ARGB clrBorder[5];
     FX_ARGB clrStart[5];
     FX_ARGB clrEnd[5];
     FX_ARGB clrFill[5];
   };
 
   void SetThemeData(uint32_t dwID);
   void SetTopLineColor(uint32_t* pData);
   void SetLeftLineColor(uint32_t* pData);
   void SetRightLineColor(uint32_t* pData);
   void SetBottomLineColor(uint32_t* pData);
   void SetBackgroudColor(uint32_t* pData);
   void SetCaptionColor(uint32_t* pData);
   void SetCornerColor(uint32_t* pData);
   int32_t GetColorID(uint32_t dwStates);
 
   struct PBThemeData* m_pThemeData;
 };
 
 #endif  // XFA_FWL_THEME_CFWL_PUSHBUTTONTP_H_