https://integration.wikimedia.org/ci/job/mediawiki-extensions-hhvm/24001/console

This test failure brought theses classes existence to my attention. They claim to implement BagOStuff (a key/value interface that stores things in class/config specific locations) but it actually defers writes. A subclass, LocalBufferedBagOStuff, also has a process-cache layer (with no time bounds) in front of a wrapped BagOStuff, which further diverges from the interface's consistency model. These should use composition instead, being their own interfaces. That would also avoid problems with core changes like https://gerrit.wikimedia.org/r/#/c/214107/ has.