Return unique_ptr from CPDF_Object::Clone().

core/fpdfapi/parser/cpdf_null.cpp

Index: core/fpdfapi/parser/cpdf_null.cpp
diff --git a/core/fpdfapi/parser/cpdf_null.cpp b/core/fpdfapi/parser/cpdf_null.cpp
index dd23101aa898e248c4a2213d064861e460e0997f..41478d7b4c00cbf225893eed6694edf68589622f 100644
--- a/core/fpdfapi/parser/cpdf_null.cpp
+++ b/core/fpdfapi/parser/cpdf_null.cpp
@@ -5,6 +5,7 @@
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "core/fpdfapi/parser/cpdf_null.h"
+#include "third_party/base/ptr_util.h"
 
 CPDF_Null::CPDF_Null() {}
 
@@ -12,6 +13,6 @@ CPDF_Object::Type CPDF_Null::GetType() const {
   return NULLOBJ;
 }
 
-CPDF_Object* CPDF_Null::Clone() const {
-  return new CPDF_Null;
+std::unique_ptr<CPDF_Object> CPDF_Null::Clone() const {
+  return pdfium::MakeUnique<CPDF_Null>();
 }