Remove NULL in xfa/

xfa/fxfa/parser/xfa_document_layout_imp.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_FXFA_PARSER_XFA_DOCUMENT_LAYOUT_IMP_H_
 #define XFA_FXFA_PARSER_XFA_DOCUMENT_LAYOUT_IMP_H_
 
 #include "xfa/fxfa/parser/xfa_doclayout.h"
 
 class CXFA_ItemLayoutProcessor;
 class CXFA_LayoutPageMgr;
 class CXFA_ContainerLayoutItem;
 
 class CXFA_LayoutProcessor {
  public:
   CXFA_LayoutProcessor(CXFA_Document* pDocument);
   ~CXFA_LayoutProcessor();
 
   CXFA_Document* GetDocument() const;
   int32_t StartLayout(FX_BOOL bForceRestart = FALSE);
-  int32_t DoLayout(IFX_Pause* pPause = NULL);
+  int32_t DoLayout(IFX_Pause* pPause = nullptr);
   FX_BOOL IncrementLayout();
   int32_t CountPages() const;
   CXFA_ContainerLayoutItem* GetPage(int32_t index) const;
   CXFA_LayoutItem* GetLayoutItem(CXFA_Node* pFormItem);
 
   void AddChangedContainer(CXFA_Node* pContainer);
   void SetForceReLayout(FX_BOOL bForceRestart) { m_bNeeLayout = bForceRestart; }
   CXFA_ContainerLayoutItem* GetRootLayoutItem() const;
   CXFA_ItemLayoutProcessor* GetRootRootItemLayoutProcessor() {
     return m_pRootItemLayoutProcessor;
   }
   CXFA_LayoutPageMgr* GetLayoutPageMgr() { return m_pLayoutPageMgr; }
 
  protected:
   void ClearLayoutData();
 
   FX_BOOL IsNeedLayout();
 
   CXFA_Document* m_pDocument;
   CXFA_ItemLayoutProcessor* m_pRootItemLayoutProcessor;
   CXFA_LayoutPageMgr* m_pLayoutPageMgr;
   CXFA_NodeArray m_rgChangedContainers;
   uint32_t m_nProgressCounter;
   FX_BOOL m_bNeeLayout;
 };
 
 #endif  // XFA_FXFA_PARSER_XFA_DOCUMENT_LAYOUT_IMP_H_