Fix some iterator invalidation issues while traversing CPDF_Dictionary.

core/src/fpdfapi/fpdf_parser/fpdf_parser_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/include/fpdfapi/fpdf_parser.h"
 
 #include <algorithm>
 #include <memory>
@@ skipping 867 matching lines @@
                 } else {
                   CPDF_Stream* pStream = pObj->AsStream();
                   if (CPDF_Dictionary* pTrailer =
                           pStream ? pStream->GetDict() : pObj->AsDictionary()) {
                     if (m_pTrailer) {
                       CPDF_Object* pRoot = pTrailer->GetElement("Root");
                       CPDF_Reference* pRef = ToReference(pRoot);
                       if (!pRoot ||
                           (pRef && IsValidObjectNumber(pRef->GetRefObjNum()) &&
                            m_ObjectInfo[pRef->GetRefObjNum()].pos != 0)) {
-                        for (const auto& it : *pTrailer) {
-                          const CFX_ByteString& key = it.first;
-                          CPDF_Object* pElement = it.second;
+                        auto it = pTrailer->begin();
+                        while (it != pTrailer->end()) {
+                          const CFX_ByteString& key = it->first;
+                          CPDF_Object* pElement = it->second;
+                          ++it;
                           FX_DWORD dwObjNum =
                               pElement ? pElement->GetObjNum() : 0;
                           if (dwObjNum) {
                             m_pTrailer->SetAtReference(key, m_pDocument,
                                                        dwObjNum);
                           } else {
                             m_pTrailer->SetAt(key, pElement->Clone());
                           }
                         }
                         pObj->Release();
@@ skipping 4105 matching lines @@
   if (!m_pLinearizedDict)
     return -1;
   CPDF_Array* pRange = m_pLinearizedDict->GetArray("H");
   if (!pRange)
     return -1;
   CPDF_Object* pStreamLen = pRange->GetElementValue(1);
   if (!pStreamLen)
     return -1;
   return pStreamLen->GetInteger();
 }