[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 37e42bc69f13cd3ba3793b6c6375d409efe0fc0e..46fc150cd7e3e1792e39c0e3071da3b9cc97eac5 100644
--- a/components/sync/test/engine/mock_connection_manager.h
+++ b/components/sync/test/engine/mock_connection_manager.h
@@ -272,6 +272,8 @@ 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,