This directory contains Human Readable Format (HRF) baseline profiles. Googlers: see go/baseline-profiles-in-chrome for more details about how this is going to be used.
These are basically the successor/sibling of android cloud profiles where a list of classes and methods are marked as (startup, hot, etc.) hinting at the ART to precompile certain parts of the dex rather than JIT for performance reasons. See https://developer.android.com/topic/performance/baselineprofiles/overview for more details.
HRF or Human Readable Format profiles is a text file containing methods and classes of your app alongside flags (startup, hot, etc). This is fairly stable across small code changes and thus can be committed to the repo/cipd. Using the macrobenchmark library you can get an HRF profile for your app. The ART can't use this though and it must be converted to a binary profile which is then shipped with your apk/bundle.