arc: Message for a low-battery case of migration notification.

chrome/browser/chromeos/arc/arc_migration_constants.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 CHROME_BROWSER_CHROMEOS_ARC_ARC_MIGRATION_CONSTANTS_H_
+#define CHROME_BROWSER_CHROMEOS_ARC_ARC_MIGRATION_CONSTANTS_H_
+
+namespace arc {
+
+// The minimum battery level to start the migration.
+constexpr double kMigrationMinimumBatteryPercent = 30;
+
+// The minimum size of available space to start the migration. (10MB)
+constexpr int64_t kMigrationMinimumAvailableStorage = 10LL * 1024 * 1024;
+
+}  // namespace arc
+
+#endif  // CHROME_BROWSER_CHROMEOS_ARC_ARC_MIGRATION_CONSTANTS_H_