Convert FWL_ERR into an enum class.

xfa/fwl/lightwidget/cfwl_scrollbar.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_LIGHTWIDGET_CFWL_SCROLLBAR_H_
 #define XFA_FWL_LIGHTWIDGET_CFWL_SCROLLBAR_H_
 
 #include "xfa/fwl/lightwidget/cfwl_widget.h"
 
 class CFWL_ScrollBar : public CFWL_Widget {
  public:
   static CFWL_ScrollBar* Create();
-  FWL_ERR Initialize(const CFWL_WidgetProperties* pProperties = NULL);
+  FWL_Error Initialize(const CFWL_WidgetProperties* pProperties = NULL);
   FX_BOOL IsVertical();
-  FWL_ERR GetRange(FX_FLOAT& fMin, FX_FLOAT& fMax);
-  FWL_ERR SetRange(FX_FLOAT fMin, FX_FLOAT fMax);
+  FWL_Error GetRange(FX_FLOAT& fMin, FX_FLOAT& fMax);
+  FWL_Error SetRange(FX_FLOAT fMin, FX_FLOAT fMax);
   FX_FLOAT GetPageSize();
-  FWL_ERR SetPageSize(FX_FLOAT fPageSize);
+  FWL_Error SetPageSize(FX_FLOAT fPageSize);
   FX_FLOAT GetStepSize();
-  FWL_ERR SetStepSize(FX_FLOAT fStepSize);
+  FWL_Error SetStepSize(FX_FLOAT fStepSize);
   FX_FLOAT GetPos();
-  FWL_ERR SetPos(FX_FLOAT fPos);
+  FWL_Error SetPos(FX_FLOAT fPos);
   FX_FLOAT GetTrackPos();
-  FWL_ERR SetTrackPos(FX_FLOAT fTrackPos);
+  FWL_Error SetTrackPos(FX_FLOAT fTrackPos);
   FX_BOOL DoScroll(uint32_t dwCode, FX_FLOAT fPos = 0.0f);
   CFWL_ScrollBar();
   virtual ~CFWL_ScrollBar();
 };
 
 #endif  // XFA_FWL_LIGHTWIDGET_CFWL_SCROLLBAR_H_