The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/35b50a0ee55f0e28aaf6076f8d9e53dfa038a545

commit 35b50a0ee55f0e28aaf6076f8d9e53dfa038a545
Author: Yafei Duan <romax@chromium.org>
Date: Fri Aug 18 00:13:38 2017

[Offline Pages] Adding new metadata fields for P2P sharing.

Added system_download_id, file_missing_time, upgrade_attempt and digest
as new metadata fields and corresponding upgrading methods. These fields
will be used by P2P sharing features.

Bug:  753472 
Change-Id: I6dfa807eb521e9565770ff2b02093be934a46ded
Reviewed-on: https://chromium-review.googlesource.com/614368
Reviewed-by: Filip Gorski <fgorski@chromium.org>
Commit-Queue: Yafei Duan <romax@chromium.org>
Cr-Commit-Position: refs/heads/master@{#495392}
[modify] https://crrev.com/35b50a0ee55f0e28aaf6076f8d9e53dfa038a545/components/offline_pages/core/offline_page_item.cc
[modify] https://crrev.com/35b50a0ee55f0e28aaf6076f8d9e53dfa038a545/components/offline_pages/core/offline_page_item.h
[modify] https://crrev.com/35b50a0ee55f0e28aaf6076f8d9e53dfa038a545/components/offline_pages/core/offline_page_metadata_store_sql.cc
[modify] https://crrev.com/35b50a0ee55f0e28aaf6076f8d9e53dfa038a545/components/offline_pages/core/offline_page_metadata_store_sql.h
[modify] https://crrev.com/35b50a0ee55f0e28aaf6076f8d9e53dfa038a545/components/offline_pages/core/offline_page_metadata_store_unittest.cc