Get rid of NULLs in fpdfsdk/

fpdfsdk/include/fsdk_annothandler.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 FPDFSDK_INCLUDE_FSDK_ANNOTHANDLER_H_
 #define FPDFSDK_INCLUDE_FSDK_ANNOTHANDLER_H_
 
 #include <map>
@@ skipping 124 matching lines @@
   virtual FX_BOOL OnKillFocus(CPDFSDK_Annot* pAnnot, uint32_t nFlag) = 0;
 #ifdef PDF_ENABLE_XFA
   virtual FX_BOOL OnXFAChangedFocus(CPDFSDK_Annot* pOldAnnot,
                                     CPDFSDK_Annot* pNewAnnot) = 0;
 #endif  // PDF_ENABLE_XFA
 };
 
 class CPDFSDK_BFAnnotHandler : public IPDFSDK_AnnotHandler {
  public:
   explicit CPDFSDK_BFAnnotHandler(CPDFDoc_Environment* pApp)
-      : m_pApp(pApp), m_pFormFiller(NULL) {}
+      : m_pApp(pApp), m_pFormFiller(nullptr) {}
   ~CPDFSDK_BFAnnotHandler() override {}
 
   // IPDFSDK_AnnotHandler
   CFX_ByteString GetType() override { return CFX_ByteString("Widget"); }
   CFX_ByteString GetName() override { return CFX_ByteString("WidgetHandler"); }
   FX_BOOL CanAnswer(CPDFSDK_Annot* pAnnot) override;
   CPDFSDK_Annot* NewAnnot(CPDF_Annot* pAnnot, CPDFSDK_PageView* pPage) override;
 #ifdef PDF_ENABLE_XFA
   CPDFSDK_Annot* NewAnnot(CXFA_FFWidget* hWidget,
                           CPDFSDK_PageView* pPage) override;
@@ skipping 92 matching lines @@
   ~CPDFSDK_XFAAnnotHandler() {}
 
  public:
   virtual CFX_ByteString GetType() { return FSDK_XFAWIDGET_TYPENAME; }
 
   virtual CFX_ByteString GetName() { return "XFAWidgetHandler"; }
 
   virtual FX_BOOL CanAnswer(CPDFSDK_Annot* pAnnot);
 
   virtual CPDFSDK_Annot* NewAnnot(CPDF_Annot* pAnnot, CPDFSDK_PageView* pPage) {
-    return NULL;
+    return nullptr;
   }
 
   virtual CPDFSDK_Annot* NewAnnot(CXFA_FFWidget* pAnnot,
                                   CPDFSDK_PageView* pPage);
 
   virtual void ReleaseAnnot(CPDFSDK_Annot* pAnnot);
 
   virtual void DeleteAnnot(CPDFSDK_Annot* pAnnot) {}
 
   virtual CFX_FloatRect GetViewBBox(CPDFSDK_PageView* pPageView,
@@ skipping 198 matching lines @@
  private:
   CPDFSDK_Annot* NextAnnot();
   CPDFSDK_Annot* PrevAnnot();
 
   std::vector<CPDFSDK_Annot*> m_iteratorAnnotList;
   const bool m_bReverse;
   size_t m_pos;
 };
 
 #endif  // FPDFSDK_INCLUDE_FSDK_ANNOTHANDLER_H_