Add the future storage framework for the BudgetDatabase.

chrome/browser/budget_service/budget_database.h

Index: chrome/browser/budget_service/budget_database.h
diff --git a/chrome/browser/budget_service/budget_database.h b/chrome/browser/budget_service/budget_database.h
new file mode 100644
index 0000000000000000000000000000000000000000..1c7c8b0c0be1b5353c80eeac43418edd2f8d1dc8
--- /dev/null
+++ b/chrome/browser/budget_service/budget_database.h
@@ -0,0 +1,51 @@
+// 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 CHROME_BROWSER_BUDGET_SERVICE_BUDGET_DATABASE_H_
+#define CHROME_BROWSER_BUDGET_SERVICE_BUDGET_DATABASE_H_
+
+#include <memory>
+
+#include "base/callback_forward.h"
+#include "base/memory/weak_ptr.h"
+#include "base/run_loop.h"
+#include "base/sequenced_task_runner.h"
+#include "components/leveldb_proto/proto_database.h"
+#include "url/gurl.h"
+
+namespace chrome_browser_budget_service {
+class Budget;
+}
+
+using chrome_browser_budget_service::Budget;

[Peter Beverloo, 2016/06/29 13:37:27]

`using` declarations in headers are forbidden by our style guide. In either
case, this shouldn't be a problem anymore when you rename it to
budget_service::Budget :)

[harkness, 2016/06/30 10:41:57]

Yes, the package names was truly horrible.

+
+class BudgetDatabase {

[Peter Beverloo, 2016/06/29 13:37:28]

++docs (why does it do what it does, why does it need the |task_runner|, ...)

[harkness, 2016/06/30 10:41:57]

Done.

+ public:
+  BudgetDatabase(const base::FilePath& database_dir,
+                 const scoped_refptr<base::SequencedTaskRunner>& task_runner);
+  ~BudgetDatabase();
+
+  // Callback for the basic GetBudget call.
+  using GetValueCallback =
+      base::Callback<void(bool success, std::unique_ptr<Budget>)>;
+
+  // Callback for setting a budget value.
+  using SetValueCallback = base::Callback<void(bool success)>;
+
+  void OnDatabaseInit(bool success);

[Peter Beverloo, 2016/06/29 13:37:27]

This should be private.

[harkness, 2016/06/30 10:41:57]

Done.

+  void GetValue(const GURL& origin, const GetValueCallback& callback);
+  void SetValue(const GURL& origin,
+                const Budget& budget,
+                const SetValueCallback& callback);
+
+ private:
+  // The database for storing budget information.
+  std::unique_ptr<leveldb_proto::ProtoDatabase<Budget>> db_;
+
+  base::WeakPtrFactory<BudgetDatabase> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(BudgetDatabase);
+};
+
+#endif  // CHROME_BROWSER_BUDGET_SERVICE_BUDGET_DATABASE_H_