Move all components/offline_pages/ files into component/offline_pages/core

components/offline_pages/offline_page_metadata_store_sql.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_METADATA_STORE_SQL_H_
-#define COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_METADATA_STORE_SQL_H_
-
-#include <stdint.h>
-
-#include <memory>
-#include <vector>
-
-#include "base/files/file_path.h"
-#include "base/memory/weak_ptr.h"
-#include "components/offline_pages/offline_page_metadata_store.h"
-
-namespace base {
-class SequencedTaskRunner;
-}
-
-namespace sql {
-class Connection;
-}
-
-namespace offline_pages {
-
-// OfflinePageMetadataStoreSQL is an instance of OfflinePageMetadataStore
-// which is implemented using a SQLite database.
-//
-// This store has a history of schema updates in pretty much every release.
-// Original schema was delivered in M52. Since then, the following changes
-// happened:
-// * In M53 expiration_time was added,
-// * In M54 title was added,
-// * In M55 we dropped the following fields (never used): version, status,
-//   offline_url, user_initiated.
-// * In M56 original_url was added.
-// * In M57 expiration_time was dropped. Existing expired pages would be
-//   removed when metadata consistency check happens.
-//
-// Here is a procedure to update the schema for this store:
-// * Decide how to detect that the store is on a particular version, which
-//   typically means that a certain field exists or is missing. This happens in
-//   Upgrade section of |CreateSchema|
-// * Work out appropriate change and apply it to all existing upgrade paths. In
-//   the interest of performing a single update of the store, it upgrades from a
-//   detected version to the current one. This means that when making a change,
-//   more than a single query may have to be updated (in case of fields being
-//   removed or needed to be initialized to a specific, non-default value).
-//   Such approach is preferred to doing N updates for every changed version on
-//   a startup after browser update.
-// * New upgrade method should specify which version it is upgrading from, e.g.
-//   |UpgradeFrom54|.
-// * Upgrade should use |UpgradeWithQuery| and simply specify SQL command to
-//   move data from old table (prefixed by temp_) to the new one.
-class OfflinePageMetadataStoreSQL : public OfflinePageMetadataStore {
- public:
-  OfflinePageMetadataStoreSQL(
-      scoped_refptr<base::SequencedTaskRunner> background_task_runner,
-      const base::FilePath& database_dir);
-  ~OfflinePageMetadataStoreSQL() override;
-
-  // Implementation methods.
-  void Initialize(const InitializeCallback& callback) override;
-  void GetOfflinePages(const LoadCallback& callback) override;
-  void AddOfflinePage(const OfflinePageItem& offline_page,
-                      const AddCallback& callback) override;
-  void UpdateOfflinePages(const std::vector<OfflinePageItem>& pages,
-                          const UpdateCallback& callback) override;
-  void RemoveOfflinePages(const std::vector<int64_t>& offline_ids,
-                          const UpdateCallback& callback) override;
-  void Reset(const ResetCallback& callback) override;
-  StoreState state() const override;
-
-  // Helper function used to force incorrect state for testing purposes.
-  void SetStateForTesting(StoreState state, bool reset_db);
-
- private:
-  // Used to conclude opening/resetting DB connection.
-  void OnOpenConnectionDone(const InitializeCallback& callback, bool success);
-  void OnResetDone(const ResetCallback& callback, bool success);
-
-  // Checks whether a valid DB connection is present and store state is LOADED.
-  bool CheckDb() const;
-
-  // Background thread where all SQL access should be run.
-  scoped_refptr<base::SequencedTaskRunner> background_task_runner_;
-
-  // Path to the database on disk.
-  base::FilePath db_file_path_;
-
-  // Database connection.
-  std::unique_ptr<sql::Connection> db_;
-
-  // State of the store.
-  StoreState state_;
-
-  base::WeakPtrFactory<OfflinePageMetadataStoreSQL> weak_ptr_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(OfflinePageMetadataStoreSQL);
-};
-
-}  // namespace offline_pages
-
-#endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_METADATA_STORE_SQL_H_