Convert FWL_ERR into an enum class.

xfa/fwl/core/fwl_appimp.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_CORE_FWL_APPIMP_H_
 #define XFA_FWL_CORE_FWL_APPIMP_H_
 
 #include <memory>
 
 #include "xfa/fwl/core/fwl_noteimp.h"
 
 class CFWL_WidgetMgr;
 class IFWL_AdapterNative;
 class IFWL_App;
 class IFWL_NoteThread;
 class IFWL_ThemeProvider;
 class IFWL_WidgetMgr;
 
 class CFWL_AppImp {
  public:
   CFWL_AppImp(IFWL_App* pIface, IFWL_AdapterNative* pAdapter);
   virtual ~CFWL_AppImp();
 
   IFWL_App* GetInterface() const { return m_pIface; }
   CFWL_NoteDriver* GetNoteDriver() const { return m_pNoteDriver.get(); }
 
-  virtual FWL_ERR Initialize();
-  virtual FWL_ERR Finalize();
+  virtual FWL_Error Initialize();
+  virtual FWL_Error Finalize();
   virtual IFWL_AdapterNative* GetAdapterNative() const;
   virtual IFWL_WidgetMgr* GetWidgetMgr() const;
   virtual IFWL_ThemeProvider* GetThemeProvider() const;
-  virtual FWL_ERR SetThemeProvider(IFWL_ThemeProvider* pThemeProvider);
-  virtual FWL_ERR Exit(int32_t iExitCode = 0);
+  virtual FWL_Error SetThemeProvider(IFWL_ThemeProvider* pThemeProvider);
+  virtual FWL_Error Exit(int32_t iExitCode = 0);
 
  protected:
   IFWL_AdapterNative* const m_pAdapterNative;
   std::unique_ptr<CFWL_WidgetMgr> m_pWidgetMgr;
   IFWL_ThemeProvider* m_pThemeProvider;
   std::unique_ptr<CFWL_NoteDriver> m_pNoteDriver;
 
  private:
   IFWL_App* const m_pIface;
 };
 
 #endif  // XFA_FWL_CORE_FWL_APPIMP_H_