I don't have a strong opinion as to where these should go. Probably src/ash since they are tied to chromeos system UI and have src/ash dependencies which would otherwise need to be provided through an interface.

+jamescook@ for direction here.

As mentioned in https://codereview.chromium.org/2596553003/#msg28, if we want to keep both the overscan calibrator and touch calibrator in the same place, then it'd be better to move the overscan calibrator out of //chrome first.

I'm OK with either //ash or //ui/display.

UI should be in ash. Other logic can go ui/display, but can stay ash if it makes things complicated.

I'd like to do some manual testing of this feature. Is there a way to manually turn on this UI, like via a flag or shortcut key? If not, how do I make it show up?

If you have a non internal touch display then you can simply enable chrome://flags#enable-touch-calibration-setting

If not, you can modify in the following 2 locations to always return true
https://cs.chromium.org/chromium/src/chrome/browser/resources/settings/device_page/display.js?q=display.js&sq=package:chromium&dr&l=267
and
https://cs.chromium.org/chromium/src/chrome/browser/extensions/display_info_provider_chromeos.cc?rcl=9a8baf4905ec918ff5da701e379758daadcac419&l=407

Both of the above approaches should bring up the "Calibrate Touchscreen" on chrome://settings/display

Also these have already been moved to src/ash under 599985.
so closing this bug.