Merge the CFWL_*Imp classes into the IFWL_* classes.

xfa/fwl/basewidget/ifwl_spinbutton.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_IFWL_SPINBUTTON_H_
-#define XFA_FWL_BASEWIDGET_IFWL_SPINBUTTON_H_
-
-#include "xfa/fwl/core/cfwl_event.h"
-#include "xfa/fxfa/cxfa_eventparam.h"
-
-#define FWL_CLASS_SpinButton L"FWL_SPINBUTTON"
-#define FWL_STYLEEXE_SPB_Vert (1L << 0)
-
-FWL_EVENT_DEF(CFWL_EvtSpbClick, CFWL_EventType::Click, FX_BOOL m_bUp;)
-
-class IFWL_SpinButton : public IFWL_Widget {
- public:
-  static IFWL_SpinButton* Create(const CFWL_WidgetImpProperties& properties,
-                                 IFWL_Widget* pOuter);
-
-  FWL_Error EnableButton(FX_BOOL bEnable, FX_BOOL bUp = TRUE);
-  FX_BOOL IsButtonEnable(FX_BOOL bUp = TRUE);
-
- protected:
-  IFWL_SpinButton();
-};
-
-#endif  // XFA_FWL_BASEWIDGET_IFWL_SPINBUTTON_H_