[Sync] Adds a new switch for enabling the new local server backend.

components/browser_sync/browser_sync_switches.cc

 // Copyright 2015 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.
 
 #include "components/browser_sync/browser_sync_switches.h"
 
 namespace switches {
 
 // Disables syncing browser data to a Google Account.
 const char kDisableSync[] = "disable-sync";
 
 // Disables syncing one or more sync data types that are on by default.
 // See sync/base/model_type.h for possible types. Types
 // should be comma separated, and follow the naming convention for string
 // representation of model types, e.g.:
 // --disable-synctypes='Typed URLs, Bookmarks, Autofill Profiles'
 const char kDisableSyncTypes[] = "disable-sync-types";
 
 // Enables synchronizing WiFi credentials across devices, using Chrome Sync.
 const char kEnableWifiCredentialSync[] = "enable-wifi-credential-sync";
 
+// Enabled the local sync backend implemented by the LoopbackServer.
+const char kEnableLocalSyncBackend[] = "enable-local-sync-backend";
+
+// Specifies the local sync backend directory. The name is chosen to mimic
+// user-data-dir etc. This flag only matters if the enable-local-sync-backend
+// flag is present.
+const char kLocalSyncBackendDir[] = "local-sync-backend-dir";
+
 }  // namespace switches