Convert FWL_ERR into an enum class.

xfa/fxfa/app/xfa_fffield.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_FFFIELD_H_
 #define XFA_FXFA_APP_XFA_FFFIELD_H_
 
 #include "xfa/fwl/core/ifwl_widgetdelegate.h"
@@ skipping 67 matching lines @@
   void CapPlacement();
   void CapTopBottomPlacement(CXFA_Caption caption,
                              const CFX_RectF& rtWidget,
                              int32_t iCapPlacement);
   void CapLeftRightPlacement(CXFA_Caption caption,
                              const CFX_RectF& rtWidget,
                              int32_t iCapPlacement);
   void SetEditScrollOffset();
 
  public:
-  virtual int32_t OnProcessMessage(CFWL_Message* pMessage);
-  virtual FWL_ERR OnProcessEvent(CFWL_Event* pEvent);
-  virtual FWL_ERR OnDrawWidget(CFX_Graphics* pGraphics,
-                               const CFX_Matrix* pMatrix = NULL);
+  virtual void OnProcessMessage(CFWL_Message* pMessage);
+  virtual void OnProcessEvent(CFWL_Event* pEvent);
+  virtual void OnDrawWidget(CFX_Graphics* pGraphics,
+                            const CFX_Matrix* pMatrix = NULL);
 
  protected:
   CFWL_Widget* m_pNormalWidget;
   CFX_RectF m_rtUI;
   CFX_RectF m_rtCaption;
 };
 
 #endif  // XFA_FXFA_APP_XFA_FFFIELD_H_