Add opaque "layout item" to widgets for caller's use.

xfa/fxfa/app/xfa_fwladapter.cpp

 // 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
 
 #include "xfa/fxfa/app/xfa_fwladapter.h"
 
 #include "xfa/fxfa/app/xfa_fffield.h"
 #include "xfa/fxfa/include/xfa_ffdoc.h"
 
 CXFA_FWLAdapterWidgetMgr::CXFA_FWLAdapterWidgetMgr() {}
 
 CXFA_FWLAdapterWidgetMgr::~CXFA_FWLAdapterWidgetMgr() {}
 
 FWL_Error CXFA_FWLAdapterWidgetMgr::RepaintWidget(IFWL_Widget* pWidget,
                                                   const CFX_RectF* pRect) {
   if (!pWidget)
     return FWL_Error::Indefinite;
 
-  CXFA_FFField* pField = (CXFA_FFField*)pWidget->GetPrivateData(pWidget);
-  if (!pField)
+  CXFA_FFWidget* pFFWidget =
+      static_cast<CXFA_FFWidget*>(pWidget->GetLayoutItem());
+  if (!pFFWidget)
     return FWL_Error::Indefinite;
 
-  pField->AddInvalidateRect(nullptr);
+  pFFWidget->AddInvalidateRect(nullptr);
   return FWL_Error::Succeeded;
 }
 
 FX_BOOL CXFA_FWLAdapterWidgetMgr::GetPopupPos(IFWL_Widget* pWidget,
                                               FX_FLOAT fMinHeight,
                                               FX_FLOAT fMaxHeight,
                                               const CFX_RectF& rtAnchor,
                                               CFX_RectF& rtPopup) {
-  CXFA_FFWidget* pFFWidget = (CXFA_FFWidget*)(pWidget->GetPrivateData(pWidget));
+  CXFA_FFWidget* pFFWidget =
+      static_cast<CXFA_FFWidget*>(pWidget->GetLayoutItem());
   CFX_Matrix mt;
   pFFWidget->GetRotateMatrix(mt);
   CFX_RectF rtRotateAnchor(rtAnchor);
   mt.TransformRect(rtRotateAnchor);
   pFFWidget->GetDoc()->GetDocProvider()->GetPopupPos(
       pFFWidget, fMinHeight, fMaxHeight, rtRotateAnchor, rtPopup);
   return TRUE;
 }