Continue IFWL widget cleanup.

xfa/fwl/core/cfwl_pushbutton.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_CFWL_PUSHBUTTON_H_
 #define XFA_FWL_CORE_CFWL_PUSHBUTTON_H_
 
 #include "xfa/fwl/core/cfwl_widget.h"
 #include "xfa/fwl/core/ifwl_pushbutton.h"
 
 class CFWL_PushButton : public CFWL_Widget, public IFWL_PushButtonDP {
  public:
   CFWL_PushButton(const IFWL_App*);
   ~CFWL_PushButton() override;
 
   void Initialize();
 
-  FWL_Error GetCaption(CFX_WideString& wsCaption);
   FWL_Error SetCaption(const CFX_WideStringC& wsCaption);
   CFX_DIBitmap* GetPicture();
   FWL_Error SetPicture(CFX_DIBitmap* pBitmap);
 
   // IFWL_DataProvider
-  FWL_Error GetCaption(IFWL_Widget* pWidget,
-                       CFX_WideString& wsCaption) override;
+  void GetCaption(IFWL_Widget* pWidget, CFX_WideString& wsCaption) override;
 
   // IFWL_PushButtonDP
   CFX_DIBitmap* GetPicture(IFWL_Widget* pWidget) override;
 
  private:
   CFX_WideString m_wsCaption;
   CFX_DIBitmap* m_pBitmap;
 };
 
 #endif  // XFA_FWL_CORE_CFWL_PUSHBUTTON_H_