[Sync] Allow sync start without sign-in if the local sync backend is on.

components/sync/test/engine/mock_connection_manager.h

Index: components/sync/test/engine/mock_connection_manager.h
diff --git a/components/sync/test/engine/mock_connection_manager.h b/components/sync/test/engine/mock_connection_manager.h
index 8f98c69a94425f01912957c6e0a481e718aa8f52..6e24f2d3f85e4f657c2355e2db3e182e2978e32c 100644
--- a/components/sync/test/engine/mock_connection_manager.h
+++ b/components/sync/test/engine/mock_connection_manager.h
@@ -268,6 +268,8 @@ class MockConnectionManager : public ServerConnectionManager {
   // Adds a new progress marker to the last update.
   sync_pb::DataTypeProgressMarker* AddUpdateProgressMarker();
 
+  void ResetAuthToken() { auth_token_.clear(); }
+
  private:
   sync_pb::SyncEntity* AddUpdateFull(syncable::Id id,
                                      syncable::Id parentid,