The component responsible for syncing user data to their account.
Docs are in [docs/website/site/developers/design-documents/sync/](https://source.chromium.org/chromium/chromium/src/+/main:docs/website/site/developers/design-documents/sync).
You can also visit them via
[chromium.org](https://www.chromium.org/developers/design-documents/sync).