cros: Add some login docs

Change-Id: I6f552db37fe1d1d7207dba715e7c613377bd67eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1588400
Commit-Queue: Jacob Dufault <jdufault@chromium.org>
Reviewed-by: Toni Baržić <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#655069}

docs/README.md

@@ -275,6 +275,9 @@ used when committed.
 *   [Running iOS test suites locally](ios/testing.md)
 
 ### Misc Chrome-OS-Specific Docs
+*   [Setting up captive portals and other restrictive networks](login/restrictive_networks.md)
+*   [Enrolling a device in OOBE/Login](login/enterprise_enrollment.md)
+*   [Debugging UI in OOBE/login/lock](login/ui_debugging.md)
 *   [Chrome Logging on Chrome OS](chrome_os_logging.md)
 
 ### Misc WebUI-Specific Docs

docs/login/enterprise_enrollment.md

@@ -0,0 +1,22 @@
+# Enterprise Enrollment on Login
+
+The easiest way to test enterprise enrollment on login is to use an actual
+enterprise account. If you don't have one, reach out a teammate; anyone with an
+account can add new accounts.
+
+Once you have an enterprise account, run chrome and [enroll the device](https://support.google.com/chrome/a/answer/1360534?hl=en). The shortcut combo is
+`Ctrl+Alt+E`.
+
+If you're testing on device and wish to clear enrollment state, the easiest way
+is to run `crossystem clear_tpm_owner_request=1` and then reboot. This clears
+TPM state which will destroy cryptohome and enrollment state. When the device
+boots next it will check and see if it needs to be force re-enrolled.
+
+Policy can be configured at admin.google.com; log in with your enterprise
+account. Whoever created the account should have granted you superuser
+privileges. You may need to log in using an incognito window if your primary
+Google account is part of an enterprise domain.
+
+When you're changing policies in admin.google.com, pay attention to the
+organization you are modifying. Try to only adjust your test organization to
+avoid propagating changes to other users.

docs/login/ui_debugging.md

@@ -0,0 +1,13 @@
+# Debugging UI
+
+The login and lock screen can run with a developer overlay that make common
+operations such as setting up a device with 10+ users trivial. Pass the flag
+`--show-login-dev-overlay` when running chrome and the UI will automatically
+appear.
+
+```sh
+./out/Release/chrome --show-login-dev-overlay
+```
+
+The overlay will use fake data where necessary to show the relevant UI; buttons
+are mostly functional but may break since fake data may be sent to chrome.