Convert FWL_ERR into an enum class.

xfa/fwl/basewidget/fwl_formproxyimp.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_FWL_FORMPROXYIMP_H_
 #define XFA_FWL_BASEWIDGET_FWL_FORMPROXYIMP_H_
 
 #include "xfa/fwl/core/fwl_formimp.h"
 #include "xfa/fwl/core/fwl_widgetimp.h"
 
 class CFWL_WidgetImpProperties;
 class CFWL_FormProxyImpDelegate;
 
 class CFWL_FormProxyImp : public CFWL_FormImp {
  public:
   CFWL_FormProxyImp(const CFWL_WidgetImpProperties& properties,
                     IFWL_Widget* pOuter);
   ~CFWL_FormProxyImp();
-  virtual FWL_ERR GetClassName(CFX_WideString& wsClass) const;
+  virtual FWL_Error GetClassName(CFX_WideString& wsClass) const;
   virtual uint32_t GetClassID() const;
   virtual FX_BOOL IsInstance(const CFX_WideStringC& wsClass) const;
-  virtual FWL_ERR Initialize();
-  virtual FWL_ERR Finalize();
-  virtual FWL_ERR Update();
-  virtual FWL_ERR DrawWidget(CFX_Graphics* pGraphics,
-                             const CFX_Matrix* pMatrix = NULL);
+  virtual FWL_Error Initialize();
+  virtual FWL_Error Finalize();
+  virtual FWL_Error Update();
+  virtual FWL_Error DrawWidget(CFX_Graphics* pGraphics,
+                               const CFX_Matrix* pMatrix = NULL);
 
  protected:
   friend class CFWL_FormProxyImpDelegate;
 };
 class CFWL_FormProxyImpDelegate : public CFWL_WidgetImpDelegate {
  public:
   CFWL_FormProxyImpDelegate(CFWL_FormProxyImp* pOwner);
-  int32_t OnProcessMessage(CFWL_Message* pMessage) override;
+  void OnProcessMessage(CFWL_Message* pMessage) override;
 
  protected:
   CFWL_FormProxyImp* m_pOwner;
 };
 
 #endif  // XFA_FWL_BASEWIDGET_FWL_FORMPROXYIMP_H_