Improve the page download:

components/offline_pages/offline_page_model_impl.h

 // Copyright 2016 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.
 
 #ifndef COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_MODEL_IMPL_H_
 #define COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_MODEL_IMPL_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 26 matching lines @@
 class GURL;
 namespace base {
 class Clock;
 class SequencedTaskRunner;
 class TimeDelta;
 class TimeTicks;
 }  // namespace base
 
 namespace offline_pages {
 
-static const int64_t kInvalidOfflineId = 0;
-
 struct ClientId;
 struct OfflinePageItem;
 
 class ArchiveManager;
 class ClientPolicyController;
 class OfflinePageStorageManager;
 
 // Implementation of service for saving pages offline, storing the offline
 // copy and metadata, and retrieving them upon request.
 class OfflinePageModelImpl : public OfflinePageModel, public KeyedService {
@@ skipping 225 matching lines @@
   base::Clock* testing_clock_;
 
   base::WeakPtrFactory<OfflinePageModelImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(OfflinePageModelImpl);
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_MODEL_IMPL_H_