Perform extra synchronization the first time `TsanNotifyWorker` hands a `RealmCoordinator` to the worker thread.
Perform extra synchronization the first time `TsanNotifyWorker` hands a `RealmCoordinator` to the worker thread.

This prevents TSan from reporting data races on members of the coordinator.

realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js