Default unspecified value added to enum in proto

chrome/browser/chromeos/policy/proto/chrome_device_policy.proto

 // Copyright 2013 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.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 package enterprise_management;
 
@@ skipping 765 matching lines @@
 // The url and hash that specified in JSON format that can be used to set the
 // device-level wallpaper on the login screen before any user logs in.
 message DeviceWallpaperImageProto {
   optional string device_wallpaper_image = 1;
 }
 
 // Migration strategy for the case when ARC(N+) needs the ext4 encryption while
 // the device used ecryptfs in the past.
 message DeviceEcryptfsMigrationStrategyProto {
   enum MigrationStrategy {
+    // Default value, unspecified.
+    UNSET = 0;
     // ARC is not allowed, no data migration needed.
-    DISALLOW_ARC = 0;
+    DISALLOW_ARC = 1;
     // The data migration is allowed, opening the possibility to use ARC.
-    ALLOW_MIGRATION = 1;
+    ALLOW_MIGRATION = 2;
   };
 
   optional MigrationStrategy migration_strategy = 1;
 }
 
 message ChromeDeviceSettingsProto {
   optional DevicePolicyRefreshRateProto device_policy_refresh_rate = 1;
   optional UserWhitelistProto user_whitelist = 2;
   optional GuestModeEnabledProto guest_mode_enabled = 3;
   optional OBSOLETE_DeviceProxySettingsProto device_proxy_settings = 4
@@ skipping 46 matching lines @@
       45;
   optional DeviceLoginScreenAppInstallListProto
       device_login_screen_app_install_list = 46;
   optional NetworkThrottlingEnabledProto network_throttling = 47;
   optional DeviceWallpaperImageProto device_wallpaper_image = 48;
   optional LoginScreenLocalesProto login_screen_locales = 49;
   optional LoginScreenInputMethodsProto login_screen_input_methods = 50;
   optional DeviceEcryptfsMigrationStrategyProto
       device_ecryptfs_migration_strategy = 51;
 }