[sync] Add typed url sync metadata to the history db

components/history/core/browser/typed_url_sync_metadata_database.h

+// Copyright 2017 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_HISTORY_CORE_BROWSER_TYPED_URL_SYNC_METADATA_DATABASE_H_
+#define COMPONENTS_HISTORY_CORE_BROWSER_TYPED_URL_SYNC_METADATA_DATABASE_H_
+
+#include "base/macros.h"
+#include "components/sync/base/model_type.h"
+#include "components/sync/model/metadata_batch.h"
+#include "sql/meta_table.h"
+
+namespace sql {
+class Connection;
+}
+
+namespace history {
+
+// A sync metadata database needs to maintain two tables: entity metadata table
+// and datatype state table. Entity metadata table contains metadata(sync
+// states) for each url. Datatype state table contains the state of typed url
+// datatype.
+class TypedURLSyncMetadataDatabase {
+ public:
+  // Must call InitVisitTable() before using to make sure the database is
+  // initialized.
+  TypedURLSyncMetadataDatabase();
+  virtual ~TypedURLSyncMetadataDatabase();
+
+  // Read all the stored metadata for typed URL and fill |metadata_batch|
+  // with it.
+  bool GetAllSyncMetadata(syncer::MetadataBatch* metadata_batch);
+
+  // Update the metadata row for typed URL, keyed by |storage_key|, to
+  // contain the contents of |metadata|.
+  bool UpdateSyncMetadata(const std::string& storage_key,

[brettw, 2017/03/20 17:27:06]

I was expecting the types here would match the database types (so this would be
an int64). Generally the row updating functions in these database classes are
pretty low-level and just provide a C++ interface to the storage.

It seems this is not hooked up so it's hard for me to see which approach is more
appropriate.

What code would be responsible for calling this function? If this is some kind
of typed URL sync adapter class, I'd rather have that adapter class do the
StringtoInt conversions.

[Gang Wu, 2017/03/20 21:34:48]

Actually, I am think about make those functions as an interface,
UpdateModelTypeState, ClearModelTypeState, UpdateMetadata and ClearMetadata, and
maybe GetAllSyncMetadata.
It seems only MetadataChangeList will call this 4 functions, here is
aotofill/autocomplete implementation,
https://cs.chromium.org/chromium/src/components/autofill/core/browser/webdata...,
so I think maybe we can unify them and make it as interface.

+                          const sync_pb::EntityMetadata& metadata);
+
+  // Remove the metadata row of typed URL keyed by |storage_key|.
+  bool ClearSyncMetadata(const std::string& storage_key);
+
+  // Update the stored sync state for the typed URL.
+  bool UpdateModelTypeState(const sync_pb::ModelTypeState& model_type_state);
+
+  // Clear the stored sync state for typed URL.
+  bool ClearModelTypeState();
+
+ protected:
+  // Returns the database for the functions in this interface.
+  virtual sql::Connection& GetDB() = 0;
+
+  // Called by the derived classes on initialization to make sure the tables
+  // and indices are properly set up. Must be called before anything else.
+  bool InitSyncTable();
+
+  sql::MetaTable* GetMetaTable() { return &meta_table_; }
+
+ private:
+  // Read all sync_pb::EntityMetadata for typed URL and fill
+  // |metadata_records| with it.
+  bool GetAllSyncEntityMetadata(syncer::EntityMetadataMap* metadata_records);
+
+  // Read sync_pb::ModelTypeState for typed URL and fill |state| with it.
+  bool GetModelTypeState(sync_pb::ModelTypeState* state);
+
+  // Own by this class, but initialed by HistoryDatabase.
+  // Check if meta_table_->GetVersionNumber() is greater than 0 to make sure
+  // meta_table_ is initialed.
+  sql::MetaTable meta_table_;
+
+  DISALLOW_COPY_AND_ASSIGN(TypedURLSyncMetadataDatabase);
+};
+
+}  // namespace history
+
+#endif  // COMPONENTS_HISTORY_CORE_BROWSER_TYPED_URL_SYNC_METADATA_DATABASE_H_