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

components/browser_sync/browser_sync_switches.cc

Index: components/browser_sync/browser_sync_switches.cc
diff --git a/components/browser_sync/browser_sync_switches.cc b/components/browser_sync/browser_sync_switches.cc
index b354cdb91c3922be6260e8d292577a65b8c18bf5..d15ad5f2c0c2be663ee33563117afe61541ebef2 100644
--- a/components/browser_sync/browser_sync_switches.cc
+++ b/components/browser_sync/browser_sync_switches.cc
@@ -19,4 +19,12 @@ 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