Reland of relax a couple checks to allow certain non-standard PDF files.

core/fpdfapi/fpdf_parser/cpdf_parser.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_parser.h"
 
 #include <vector>
 
@@ skipping 1059 matching lines @@
     dwCaculatedSize *= totalWidth;
     if (!dwCaculatedSize.IsValid() ||
         dwCaculatedSize.ValueOrDie() > dwTotalSize) {
       continue;
     }
 
     const uint8_t* segstart = pData + segindex * totalWidth;
     FX_SAFE_UINT32 dwMaxObjNum = startnum;
     dwMaxObjNum += count;
     uint32_t dwV5Size = m_ObjectInfo.empty() ? 0 : GetLastObjNum() + 1;
-    if (!dwMaxObjNum.IsValid() || dwMaxObjNum.ValueOrDie() > dwV5Size)
+    if (!dwMaxObjNum.IsValid())
       continue;
+    // When the max object number is larger than the defined size, try to
+    // increase the size to accomodate more objects.
+    // Some software messes this up, see chromium:596947.
+    if (dwMaxObjNum.ValueOrDie() > dwV5Size)
+      ShrinkObjectMap(dwMaxObjNum.ValueOrDie());
 
     for (uint32_t j = 0; j < count; j++) {
       int32_t type = 1;
       const uint8_t* entrystart = segstart + j * totalWidth;
       if (WidthArray[0])
         type = GetVarInt(entrystart, WidthArray[0]);
 
       if (GetObjectType(startnum + j) == 255) {
         FX_FILESIZE offset =
             GetVarInt(entrystart + WidthArray[0], WidthArray[1]);
@@ skipping 578 matching lines @@
   if (!LoadLinearizedAllCrossRefV4(m_LastXRefOffset, m_dwXrefStartObjNum) &&
       !LoadLinearizedAllCrossRefV5(m_LastXRefOffset)) {
     m_LastXRefOffset = 0;
     m_pSyntax->m_MetadataObjnum = dwSaveMetadataObjnum;
     return FORMAT_ERROR;
   }
 
   m_pSyntax->m_MetadataObjnum = dwSaveMetadataObjnum;
   return SUCCESS;
 }