Code change to avoid signed/unsigned mismatch warnings

core/fpdfapi/fpdf_parser/include/cpdf_object.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_FPDF_PARSER_INCLUDE_CPDF_OBJECT_H_
 #define CORE_FPDFAPI_FPDF_PARSER_INCLUDE_CPDF_OBJECT_H_
 
 #include "core/fxcrt/include/fx_string.h"
 #include "core/fxcrt/include/fx_system.h"
 
 class CPDF_Array;
 class CPDF_Boolean;
 class CPDF_Dictionary;
 class CPDF_Name;
 class CPDF_Null;
 class CPDF_Number;
 class CPDF_Reference;
 class CPDF_Stream;
 class CPDF_String;
 
 class CPDF_Object {
  public:
+  static const uint32_t kInvalidObjNum = static_cast<uint32_t>(-1);
   enum Type {
     BOOLEAN = 1,
     NUMBER,
     STRING,
     NAME,
     ARRAY,
     DICTIONARY,
     STREAM,
     NULLOBJ,
     REFERENCE
@@ skipping 117 matching lines @@
 
 inline CPDF_Stream* ToStream(CPDF_Object* obj) {
   return obj ? obj->AsStream() : nullptr;
 }
 
 inline const CPDF_Stream* ToStream(const CPDF_Object* obj) {
   return obj ? obj->AsStream() : nullptr;
 }
 
 #endif  // CORE_FPDFAPI_FPDF_PARSER_INCLUDE_CPDF_OBJECT_H_