Remove CPDF_Object::GetConstString and overrides

core/fpdfapi/fpdf_page/fpdf_page_parser.cpp

 // Copyright 2014 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_page/pageint.h"
 
 #include <vector>
 
@@ skipping 718 matching lines @@
     if (m_pDocument->IsFormStream(pRes->GetRefObjNum(), bForm) && !bForm)
       return;
   }
 
   CPDF_Stream* pXObject = ToStream(FindResourceObj("XObject", name));
   if (!pXObject) {
     m_bResourceMissing = TRUE;
     return;
   }
 
-  CFX_ByteStringC type = pXObject->GetDict()
-                             ? pXObject->GetDict()->GetConstStringBy("Subtype")
-                             : CFX_ByteStringC();
+  CFX_ByteString type;
+  if (pXObject->GetDict())
+    type = pXObject->GetDict()->GetStringBy("Subtype");
+
   if (type == "Image") {
     if (m_Options.m_bTextOnly) {
       return;
     }
     CPDF_ImageObject* pObj = AddImage(pXObject, NULL, FALSE);
     m_LastImageName = name;
     m_pLastImage = pObj->m_pImage;
     if (!m_pObjectHolder->HasImageMask())
       m_pObjectHolder->SetHasImageMask(m_pLastImage->IsMask());
   } else if (type == "Form") {
@@ skipping 1062 matching lines @@
         } else {
           PDF_ReplaceAbbr(pElement);
         }
       }
       break;
     }
     default:
       break;
   }
 }