Cleanup unused methods and return values in FWL code.

xfa/fwl/core/ifwl_datetimecalendar.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_IFWL_DATETIMECALENDAR_H_
 #define XFA_FWL_CORE_IFWL_DATETIMECALENDAR_H_
 
 #include "xfa/fwl/core/ifwl_monthcalendar.h"
 
 class IFWL_DateTimeCalendar : public IFWL_MonthCalendar {
  public:
   IFWL_DateTimeCalendar(const CFWL_WidgetImpProperties& properties,
                         IFWL_Widget* pOuter);
 
   // IFWL_MonthCalendar
   FWL_Error Initialize() override;
-  FWL_Error Finalize() override;
+  void Finalize() override;
 
  protected:
   friend class CFWL_DateTimeCalendarImpDelegate;
 };
 
 class CFWL_DateTimeCalendarImpDelegate : public CFWL_MonthCalendarImpDelegate {
  public:
   CFWL_DateTimeCalendarImpDelegate(IFWL_DateTimeCalendar* pOwner);
   void OnProcessMessage(CFWL_Message* pMessage) override;
 
   void OnLButtonDownEx(CFWL_MsgMouse* pMsg);
   void OnLButtonUpEx(CFWL_MsgMouse* pMsg);
   void OnMouseMoveEx(CFWL_MsgMouse* pMsg);
 
  protected:
   IFWL_DateTimeCalendar* m_pOwner;
   FX_BOOL m_bFlag;
 
  private:
   void DisForm_OnProcessMessage(CFWL_Message* pMessage);
   void DisForm_OnLButtonUpEx(CFWL_MsgMouse* pMsg);
 };
 
 #endif  // XFA_FWL_CORE_IFWL_DATETIMECALENDAR_H_