Summary:
This interface is redundant and has been deprecated for a while.
It's also unused internally. Let's delete it.
I moved the comments to the corresponding functions in BackupEngine/
BackupEngineReadOnly. This caused the diff tool to not work cleanly.
Test Plan:
unit tests
$ ./backupable_db_test
Reviewers: yhchiang, sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D56331