Add support of rebuilding crossrefs with compressed objects.

Change-Id: I0743c34f0206f85828570430edb9f62b6b0cdbb5
Reviewed-on: https://pdfium-review.googlesource.com/37315
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Art Snake <art-snake@yandex-team.ru>

core/fpdfapi/parser/cpdf_object_stream.h

diff --git a/core/fpdfapi/parser/cpdf_object_stream.h b/core/fpdfapi/parser/cpdf_object_stream.h
index 816c1be..44aa8f7 100644
--- a/core/fpdfapi/parser/cpdf_object_stream.h
+++ b/core/fpdfapi/parser/cpdf_object_stream.h
@@ -33,6 +33,9 @@
   bool HasObject(uint32_t obj_number) const;
   std::unique_ptr<CPDF_Object> ParseObject(CPDF_IndirectObjectHolder* pObjList,
                                            uint32_t obj_number) const;
+  const std::map<uint32_t, uint32_t>& objects_offsets() const {
+    return objects_offsets_;
+  }
 
  protected:
   explicit CPDF_ObjectStream(const CPDF_Stream* stream);