This directory contains components that are used by //ash system UI and window manager code. It sits “below” //ash in the dependency graph. For C++ code, think of //ash/components like top-level //components, but for code that is only used on Chrome OS, and only for system UI / window manager support.
For example, //ash/components/account_manager manages the user's GAIA accounts, but only on behalf of Chrome OS code. //components/account_manager_core contains cross-platform support for accounts.
Much of this code used to live in //chromeos/components. The Lacros project is extracting browser functionality into a separate binary. As part of this migration, code used only by the ash-chrome system UI binary moved into “ash” directories. See the Chrome OS source directory migration design doc for details.