Revert "Make CPDF_Object containers hold objects via unique pointers."

core/fpdfapi/parser/cpdf_reference.h

 // Copyright 2016 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 CORE_FPDFAPI_PARSER_CPDF_REFERENCE_H_
 #define CORE_FPDFAPI_PARSER_CPDF_REFERENCE_H_
 
 #include <set>
@@ skipping 29 matching lines @@
   CPDF_Object* CloneNonCyclic(
       bool bDirect,
       std::set<const CPDF_Object*>* pVisited) const override;
 
   CPDF_Object* SafeGetDirect() const;
 
   CPDF_IndirectObjectHolder* m_pObjList;
   uint32_t m_RefObjNum;
 };
 
-using UniqueReference =
-    std::unique_ptr<CPDF_Reference, ReleaseDeleter<CPDF_Object>>;
-
 inline CPDF_Reference* ToReference(CPDF_Object* obj) {
   return obj ? obj->AsReference() : nullptr;
 }
 
 inline const CPDF_Reference* ToReference(const CPDF_Object* obj) {
   return obj ? obj->AsReference() : nullptr;
 }
 
 #endif  // CORE_FPDFAPI_PARSER_CPDF_REFERENCE_H_