Summary:
`last_stats_dump_time_microsec_` is not used after initialization.
I guess that it was previously used to implement periodically dumping stats,
but this functionality has now been delegated to the `PeriodicTaskScheduler`.
4b79e8c003/db/db_impl/db_impl.cc (L770-L778)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/11824
Reviewed By: cbi42
Differential Revision: D49278311
Pulled By: jowlyzhang
fbshipit-source-id: 5856245580afc026e6b490755a45c5436a2375c9
84d335b619