Remove NULL in xfa/

xfa/fwl/basewidget/fwl_pushbuttonimp.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_FWL_PUSHBUTTONIMP_H_
 #define XFA_FWL_BASEWIDGET_FWL_PUSHBUTTONIMP_H_
 
 #include "xfa/fwl/core/fwl_widgetimp.h"
@@ skipping 39 matching lines @@
   uint32_t m_dwTTOStyles;
   int32_t m_iTTOAlign;
 };
 
 class CFWL_PushButtonImpDelegate : public CFWL_WidgetImpDelegate {
  public:
   CFWL_PushButtonImpDelegate(CFWL_PushButtonImp* pOwner);
   void OnProcessMessage(CFWL_Message* pMessage) override;
   void OnProcessEvent(CFWL_Event* pEvent) override;
   void OnDrawWidget(CFX_Graphics* pGraphics,
-                    const CFX_Matrix* pMatrix = NULL) override;
+                    const CFX_Matrix* pMatrix = nullptr) override;
 
  protected:
   void OnFocusChanged(CFWL_Message* pMsg, FX_BOOL bSet = TRUE);
   void OnLButtonDown(CFWL_MsgMouse* pMsg);
   void OnLButtonUp(CFWL_MsgMouse* pMsg);
   void OnMouseMove(CFWL_MsgMouse* pMsg);
   void OnMouseLeave(CFWL_MsgMouse* pMsg);
   void OnKeyDown(CFWL_MsgKey* pMsg);
   CFWL_PushButtonImp* m_pOwner;
 };
 
 #endif  // XFA_FWL_BASEWIDGET_FWL_PUSHBUTTONIMP_H_