Fix missing OfflinePageItem file_size equality check.

Bug: 833008
Change-Id: Ie97bd09ba7aa65bf56532790ee0200ae72fd5383
Reviewed-on: https://chromium-review.googlesource.com/1015970Reviewed-by: Yafei Duan <romax@chromium.org>
Commit-Queue: Carlos Knippschild <carlosk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551546}

components/offline_pages/core/offline_page_item.cc

@@ -74,7 +74,7 @@ OfflinePageItem::~OfflinePageItem() {}
 bool OfflinePageItem::operator==(const OfflinePageItem& other) const {
   return url == other.url && offline_id == other.offline_id &&
          client_id == other.client_id && file_path == other.file_path &&
-         creation_time == other.creation_time &&
+         file_size == other.file_size && creation_time == other.creation_time &&
          last_access_time == other.last_access_time &&
          access_count == other.access_count && title == other.title &&
          flags == other.flags && original_url == other.original_url &&