Adding a SQL implementation of the backing store for previews opt outs

components/previews/core/previews_opt_out_store_sql.h

Index: components/previews/core/previews_opt_out_store_sql.h
diff --git a/components/previews/core/previews_opt_out_store_sql.h b/components/previews/core/previews_opt_out_store_sql.h
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+++ b/components/previews/core/previews_opt_out_store_sql.h
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+// 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_PREVIEWS_PREVIEWS_OPT_OUT_STORE_SQL_H_
+#define COMPONENTS_PREVIEWS_PREVIEWS_OPT_OUT_STORE_SQL_H_
+
+#include <stdint.h>
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/files/file_path.h"
+#include "base/threading/thread_checker.h"
+#include "components/previews/core/previews_opt_out_store.h"
+
+namespace base {
+class SequencedTaskRunner;
+class SingleThreadTaskRunner;
+}
+
+namespace sql {
+class Connection;
+}
+
+namespace previews {
+
+// PreviewsOptOutStoreSQL is an instance of PreviewsOptOutStore
+// which is implemented using a SQLite database.
+class PreviewsOptOutStoreSQL : public PreviewsOptOutStore {
+ public:
+  PreviewsOptOutStoreSQL(
+      scoped_refptr<base::SingleThreadTaskRunner> io_task_runner,
+      scoped_refptr<base::SequencedTaskRunner> background_task_runner,
+      const base::FilePath& database_dir);
+  ~PreviewsOptOutStoreSQL() override;
+
+  // PreviewsOptOutStore implementation:
+  void AddPreviewNavigation(bool opt_out,
+                            const std::string& host_name,
+                            PreviewsType type,
+                            base::Time now) override;
+  void LoadBlackList(LoadBlackListCallback callback) override;
+
+ private:
+  // Thread this object is accessed on.
+  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+
+  // Background thread where all SQL access should be run.
+  scoped_refptr<base::SequencedTaskRunner> background_task_runner_;
+
+  // Path to the database on disk.
+  const base::FilePath db_file_path_;
+
+  // SQL connection to the SQLite database.
+  std::unique_ptr<sql::Connection> db_;
+
+  // Whether the database initialization was started yet.
+  bool initialized_;
+
+  DISALLOW_COPY_AND_ASSIGN(PreviewsOptOutStoreSQL);
+};
+
+}  // namespace previews
+
+#endif  // COMPONENTS_PREVIEWS_PREVIEWS_OPT_OUT_STORE_SQL_H_