Remove CPDF_Object::GetConstString and overrides

core/fpdfapi/fpdf_parser/cpdf_object.cpp

 // 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
 
 #include "core/fpdfapi/fpdf_parser/include/cpdf_object.h"
 
 #include <algorithm>
 
@@ skipping 15 matching lines @@
   if (m_ObjNum)
     return;
 
   Destroy();
 }
 
 CFX_ByteString CPDF_Object::GetString() const {
   return CFX_ByteString();
 }
 
-CFX_ByteStringC CPDF_Object::GetConstString() const {
-  return CFX_ByteStringC();
-}
-
 CFX_WideString CPDF_Object::GetUnicodeText() const {
   return CFX_WideString();
 }
 
 FX_FLOAT CPDF_Object::GetNumber() const {
   return 0;
 }
 
 int CPDF_Object::GetInteger() const {
   return 0;
@@ skipping 99 matching lines @@
   return nullptr;
 }
 
 CPDF_String* CPDF_Object::AsString() {
   return nullptr;
 }
 
 const CPDF_String* CPDF_Object::AsString() const {
   return nullptr;
 }