Make CPDF_Object subclass constructors intern strings

core/fpdfapi/parser/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_PARSER_CPDF_OBJECT_H_
 #define CORE_FPDFAPI_PARSER_CPDF_OBJECT_H_
 
 #include <memory>
 #include <set>
+#include <type_traits>
 
 #include "core/fxcrt/fx_string.h"
 #include "core/fxcrt/fx_system.h"
 
 class CPDF_Array;
 class CPDF_Boolean;
 class CPDF_Dictionary;
 class CPDF_Name;
 class CPDF_Null;
 class CPDF_Number;
@@ skipping 88 matching lines @@
       bool bDirect,
       std::set<const CPDF_Object*>* pVisited) const;
 
   uint32_t m_ObjNum;
   uint32_t m_GenNum;
 
  private:
   CPDF_Object(const CPDF_Object& src) {}
 };
 
+template <typename T>
+struct CanInternStrings {
+  static const bool value = std::is_same<T, CPDF_Array>::value ||
+                            std::is_same<T, CPDF_Dictionary>::value ||
+                            std::is_same<T, CPDF_Name>::value ||
+                            std::is_same<T, CPDF_String>::value;
+};
+
 #endif  // CORE_FPDFAPI_PARSER_CPDF_OBJECT_H_