Revert of delete the levelDB storage implementation.

components/offline_pages/offline_page_model.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_model.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/files/file_util.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/optional.h"
 #include "base/rand_util.h"
 #include "base/sequenced_task_runner.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "components/offline_pages/archive_manager.h"
 #include "components/offline_pages/client_policy_controller.h"
 #include "components/offline_pages/offline_page_item.h"
 #include "components/offline_pages/offline_page_storage_manager.h"
+#include "components/offline_pages/proto/offline_pages.pb.h"
 #include "url/gurl.h"
 
 using ArchiverResult = offline_pages::OfflinePageArchiver::ArchiverResult;
 
 namespace offline_pages {
 
 namespace {
 
 // This enum is used in an UMA histogram. Hence the entries here shouldn't
 // be deleted or re-ordered and new ones should be added to the end.
@@ skipping 790 matching lines @@
 void OfflinePageModel::RunWhenLoaded(const base::Closure& task) {
   if (!is_loaded_) {
     delayed_tasks_.push_back(task);
     return;
   }
 
   base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE, task);
 }
 
 }  // namespace offline_pages