Add type cast definitions for CPDF_Stream.

core/src/fpdfapi/fpdf_parser/fpdf_parser_utility.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 "../../../include/fpdfapi/fpdf_parser.h"
 const char PDF_CharType[256] = {
     // NUL  SOH  STX  ETX  EOT  ENQ  ACK  BEL  BS   HT   LF   VT   FF   CR   SO
     // SI
@@ skipping 399 matching lines @@
         if (pValue && pValue->GetObjNum()) {
           buf << " " << pValue->GetObjNum() << FX_BSTRC(" 0 R ");
         } else {
           buf << pValue;
         }
       }
       buf << FX_BSTRC(">>");
       break;
     }
     case PDFOBJ_STREAM: {
-      CPDF_Stream* p = (CPDF_Stream*)pObj;
+      const CPDF_Stream* p = pObj->AsStream();
       buf << p->GetDict() << FX_BSTRC("stream\r\n");
       CPDF_StreamAcc acc;
       acc.LoadAllData(p, TRUE);
       buf.AppendBlock(acc.GetData(), acc.GetSize());
       buf << FX_BSTRC("\r\nendstream");
       break;
     }
     default:
       ASSERT(FALSE);
       break;
@@ skipping 41 matching lines @@
     CPDF_Object* pFound = SearchNumberNode(pKid, num);
     if (pFound) {
       return pFound;
     }
   }
   return NULL;
 }
 CPDF_Object* CPDF_NumberTree::LookupValue(int num) {
   return SearchNumberNode(m_pRoot, num);
 }