“Early prefs” is the mechanism to export some of the Profile preferences in a way that they can be read early in the ChromeOS Login flow, before Profile loading starts.

EarlyPrefsWriter can be used to export policies from the Profile. It works in a write-only mode, replacing previous data, so all relevant values should be re-exported every time.

Version 1 of the schema:

• schema_version (int)
• data : dict from pref name to pref value and some metadata
  • managed (bool)
  • recommended (bool), defined only for managed prefs
  • value (base::Value) actual value of the pref