Revert of delete the levelDB storage implementation.

components/offline_pages/offline_page_metadata_store_impl.h

Index: components/offline_pages/offline_page_metadata_store_impl.h
diff --git a/components/offline_pages/offline_page_metadata_store_impl.h b/components/offline_pages/offline_page_metadata_store_impl.h
new file mode 100644
index 0000000000000000000000000000000000000000..6b59794d1c0a5efbbdf7457002e5016f0f319429
--- /dev/null
+++ b/components/offline_pages/offline_page_metadata_store_impl.h
@@ -0,0 +1,90 @@
+// 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.
+
+#ifndef COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_METADATA_STORE_IMPL_H_
+#define COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_METADATA_STORE_IMPL_H_
+
+#include <stdint.h>
+
+#include <vector>
+
+#include "base/files/file_path.h"
+#include "base/gtest_prod_util.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "components/leveldb_proto/proto_database.h"
+#include "components/offline_pages/offline_page_metadata_store.h"
+
+namespace base {
+class SequencedTaskRunner;
+}
+
+namespace offline_pages {
+
+class OfflinePageEntry;
+
+// Implements OfflinePageMetadataStore using leveldb_proto::ProtoDatabase
+// component. Stores metadata of offline pages as serialized protobufs in a
+// LevelDB key/value pairs.
+// Underlying implementation guarantees that all of the method calls will be
+// executed sequentially, and started operations will finish even after the
+// store is already destroyed (callbacks will be called).
+class OfflinePageMetadataStoreImpl : public OfflinePageMetadataStore {
+ public:
+  OfflinePageMetadataStoreImpl(
+      scoped_refptr<base::SequencedTaskRunner> background_task_runner,
+      const base::FilePath& database_dir);
+  ~OfflinePageMetadataStoreImpl() override;
+
+  // OfflinePageMetadataStore implementation:
+  void Load(const LoadCallback& callback) override;
+  void AddOrUpdateOfflinePage(const OfflinePageItem& offline_page_record,
+                              const UpdateCallback& callback) override;
+  void RemoveOfflinePages(const std::vector<int64_t>& offline_ids,
+                          const UpdateCallback& callback) override;
+  void Reset(const ResetCallback& callback) override;
+
+ private:
+  friend class OfflinePageMetadataStoreImplTest;
+
+  void LoadContinuation(const LoadCallback& callback, bool success);
+  void LoadDone(const LoadCallback& callback,
+                bool success,
+                std::unique_ptr<std::vector<OfflinePageEntry>> entries);
+  void NotifyLoadResult(const LoadCallback& callback,
+                        LoadStatus status,
+                        const std::vector<OfflinePageItem>& result);
+
+  // Implements the update.
+  void UpdateEntries(std::unique_ptr<leveldb_proto::ProtoDatabase<
+                         OfflinePageEntry>::KeyEntryVector> entries_to_save,
+                     std::unique_ptr<std::vector<std::string>> keys_to_remove,
+                     const UpdateCallback& callback);
+
+  void UpdateDone(const OfflinePageMetadataStore::UpdateCallback& callback,
+                  bool success);
+
+  void ResetDone(const ResetCallback& callback, bool success);
+
+  // Called when a database has to be migrated from old bookmark ids
+  // to new offline ids.
+  // TODO(bburns): Perhaps remove this eventually?
+  void DatabaseUpdateDone(const OfflinePageMetadataStore::LoadCallback& cb,
+                          LoadStatus status,
+                          const std::vector<OfflinePageItem>& result,
+                          bool success);
+
+  scoped_refptr<base::SequencedTaskRunner> background_task_runner_;
+  base::FilePath database_dir_;
+  std::unique_ptr<leveldb_proto::ProtoDatabase<OfflinePageEntry>> database_;
+
+  base::WeakPtrFactory<OfflinePageMetadataStoreImpl> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(OfflinePageMetadataStoreImpl);
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_METADATA_STORE_IMPL_H_