This directory provides support for Site Isolation that cannot live in //content yet needs to be shared across platforms that may not necessarily include //chrome. This mostly includes mechanisms for partial Site Isolation, such as loading the built-in list of isolated sites, managing preferences that store heuristically isolated sites where users have entered passwords or logged in via OAuth, and computing memory thresholds for applying Site Isolation. Platforms that currently use partial Site Isolation include Android, Fuchsia, WebLayer, and Blink for iOS, while iOS (with Webkit) does not support Site Isolation at all. See process_model_and_site_isolation.md for more details.
Most of the core Site Isolation code can be found in content/browser/.