Convert FWL_ERR into an enum class.

xfa/fwl/lightwidget/cfwl_widgetdelegate.cpp

 // Copyright 2016 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
 
 #include "xfa/fwl/lightwidget/cfwl_widgetdelegate.h"
 
 #include "xfa/fwl/core/cfwl_event.h"
 #include "xfa/fwl/core/cfwl_message.h"
 
 CFWL_WidgetDelegate::CFWL_WidgetDelegate() {}
 
 CFWL_WidgetDelegate::~CFWL_WidgetDelegate() {}
 
-int32_t CFWL_WidgetDelegate::OnProcessMessage(CFWL_Message* pMessage) {
-  return 1;
-}
+void CFWL_WidgetDelegate::OnProcessMessage(CFWL_Message* pMessage) {}
 
-FWL_ERR CFWL_WidgetDelegate::OnProcessEvent(CFWL_Event* pEvent) {
-  return FWL_ERR_Succeeded;
-}
+void CFWL_WidgetDelegate::OnProcessEvent(CFWL_Event* pEvent) {}
 
-FWL_ERR CFWL_WidgetDelegate::OnDrawWidget(CFX_Graphics* pGraphics,
-                                          const CFX_Matrix* pMatrix) {
-  return FWL_ERR_Succeeded;
-}
+void CFWL_WidgetDelegate::OnDrawWidget(CFX_Graphics* pGraphics,
+                                       const CFX_Matrix* pMatrix) {}