Get rid of NULLs in xfa/

xfa/fxfa/app/xfa_ffpushbutton.h

Index: xfa/fxfa/app/xfa_ffpushbutton.h
diff --git a/xfa/fxfa/app/xfa_ffpushbutton.h b/xfa/fxfa/app/xfa_ffpushbutton.h
index 96cf785eb0f9fda2634e3ee3ba8e6232123306af..537c409680e37130dad383ff60f141f0a1ffb6f3 100644
--- a/xfa/fxfa/app/xfa_ffpushbutton.h
+++ b/xfa/fxfa/app/xfa_ffpushbutton.h
@@ -21,7 +21,7 @@ class CXFA_FFPushButton : public CXFA_FFField {
   CXFA_FFPushButton(CXFA_FFPageView* pPageView, CXFA_WidgetAcc* pDataAcc);
   virtual ~CXFA_FFPushButton();
   virtual void RenderWidget(CFX_Graphics* pGS,
-                            CFX_Matrix* pMatrix = NULL,
+                            CFX_Matrix* pMatrix = nullptr,
                             uint32_t dwStatus = 0,
                             int32_t iRotate = 0);
   virtual FX_BOOL LoadWidget();
@@ -31,12 +31,12 @@ class CXFA_FFPushButton : public CXFA_FFField {
   virtual void OnProcessMessage(CFWL_Message* pMessage);
   virtual void OnProcessEvent(CFWL_Event* pEvent);
   virtual void OnDrawWidget(CFX_Graphics* pGraphics,
-                            const CFX_Matrix* pMatrix = NULL);
+                            const CFX_Matrix* pMatrix = nullptr);
 
  protected:
   void LoadHighlightCaption();
   void LayoutHighlightCaption();
-  void RenderHighlightCaption(CFX_Graphics* pGS, CFX_Matrix* pMatrix = NULL);
+  void RenderHighlightCaption(CFX_Graphics* pGS, CFX_Matrix* pMatrix = nullptr);
   FX_FLOAT GetLineWidth();
   FX_ARGB GetLineColor();
   FX_ARGB GetFillColor();