[Offline Pages] Removes two-step expiration related.

components/offline_pages/offline_page_item.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/offline_pages/offline_page_item.h"
 
 namespace offline_pages {
 
 ClientId::ClientId() : name_space(""), id("") {}
 
@@ skipping 48 matching lines @@
 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 &&
          last_access_time == other.last_access_time &&
-         expiration_time == other.expiration_time &&
          access_count == other.access_count &&
          title == other.title &&
          flags == other.flags &&
          original_url == other.original_url;
 }
 
-bool OfflinePageItem::IsExpired() const {
-  return creation_time < expiration_time;
-}
-
 }  // namespace offline_pages