Remove include only fwl.h and IWYU.

xfa/include/fwl/lightwidget/checkbox.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_INCLUDE_FWL_LIGHTWIDGET_CHECKBOX_H_
 #define XFA_INCLUDE_FWL_LIGHTWIDGET_CHECKBOX_H_
 
-class CFWL_Widget;
-class CFWL_WidgetProperties;
-class IFWL_CheckBoxDP;
-class CFWL_CheckBox;
-class CFWL_CheckBoxDP;
+#include "xfa/include/fwl/basewidget/fwl_checkbox.h"
+#include "xfa/include/fwl/lightwidget/widget.h"
+
 class CFWL_CheckBox : public CFWL_Widget {
  public:
   static CFWL_CheckBox* Create();
 
   FWL_ERR Initialize(const CFWL_WidgetProperties* pProperties = NULL);
   FWL_ERR GetCaption(CFX_WideString& wsCaption);
   FWL_ERR SetCaption(const CFX_WideStringC& wsCaption);
   FWL_ERR SetBoxSize(FX_FLOAT fHeight);
   int32_t GetCheckState();
   FWL_ERR SetCheckState(int32_t iCheck);
   CFWL_CheckBox();
   virtual ~CFWL_CheckBox();
 
  protected:
   class CFWL_CheckBoxDP : public IFWL_CheckBoxDP {
    public:
     CFWL_CheckBoxDP();
     virtual FWL_ERR GetCaption(IFWL_Widget* pWidget, CFX_WideString& wsCaption);
     virtual FX_FLOAT GetBoxSize(IFWL_Widget* pWidget);
     FX_FLOAT m_fBoxHeight;
     CFX_WideString m_wsCaption;
   };
   CFWL_CheckBoxDP m_checkboxData;
 };
 
 #endif  // XFA_INCLUDE_FWL_LIGHTWIDGET_CHECKBOX_H_