Should we be restricting Kiosk APIs only to auto-launched sessions?
The reasoning behind allowing Kiosk APIs more access is that there is no other user using the machine - which may not be true in the case of non-auto-launched kiosk-mode?

Non-auto-launched kiosk also runs in its own session and in a locked down env (i.e. no other uses) similar to the auto launched ones. Just that it is launched manually.

Yeah, I think there are APIs that make sense in non-autolaunched kiosk (e.g. audio).

For networking, I'm a little torn about whether to allow it in non auto-launched kiosk or not - main concern would be enabling kiosk app to change system wide network configs, something that should be more expected to be possible when the device is set up primarily to launch a kiosk app.
(plus, use cases for the API are bound to auto-launched kiosk devices)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5babfd313562ebd60a9a7910912a764bed6d63c0

commit 5babfd313562ebd60a9a7910912a764bed6d63c0
Author: tbarzic <tbarzic@chromium.org>
Date: Tue Jan 10 20:13:18 2017

Introduce kiosk.autolaunched feature session type

The session type will be used to restrict extension features to
auto-launched kiosk sessions - kiosk session that are launched
automatically from the login screen, without user interaction.

To be able properly est auto launched flag, browser process
feature session type initialization is moved to
AppLaunchController, class which controls kiosk app launch.

Also, move browser process feature session type initialization
from ChromeUserManager::UpdateLoginState to
UserSessionManager::PerformPostUserLoggedInActions (for regular
users), which seems like a more suitable place.

BUG= 676213 

Review-Url: https://codereview.chromium.org/2601803003
Cr-Commit-Position: refs/heads/master@{#442667}

[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/chrome/browser/chromeos/login/app_launch_controller.cc
[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/chrome/browser/chromeos/login/session/user_session_manager.cc
[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/chrome/browser/chromeos/login/session/user_session_manager.h
[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/chrome/browser/chromeos/login/users/chrome_user_manager_impl.cc
[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/chrome/common/extensions/api/_features.md
[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/chrome/common/extensions/api/common_extension_api_unittest.cc
[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/chrome/test/data/extensions/extension_api_unittest/api_features.json
[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/extensions/common/features/feature_session_type.h
[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/extensions/common/features/simple_feature.cc
[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/extensions/common/features/simple_feature.h
[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/extensions/common/features/simple_feature_unittest.cc
[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/extensions/common/permissions/usb_device_permission_unittest.cc
[modify] https://crrev.com/5babfd313562ebd60a9a7910912a764bed6d63c0/tools/json_schema_compiler/feature_compiler.py