See https://cs.chromium.org/chromium/src/ui/webui/resources/cr_components/README.md. 

IIRC, only elements that are used by stand-alone WebUI dialogs are meant to be moved to cr_components. IS the "lock screen" UI you are mentioning a similar case?

re #1

The lock screen is in the category of "login" in the link. The login/lock screens are now view based, but they still show the webui versions sometimes, and there is also a flag to enable the webui versions full time.

cr_components was originally created to share components between settings
and dialogs, but sharing between settings and lock screen (or any two
separate pages) is equally valid.

#2
> still show the webui versions sometimes

How reasonable is it to remove the remaining uses of the webui version?

#4

+jdufault

I think the current use of the webui pin_keyboard is going to be removed soonish, but there are talks of OOBE using pin_keyboard to set up PIN as while they set up chromebook.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/30f895bc5ffa144a1feb16419f4adbe9c56bb179

commit 30f895bc5ffa144a1feb16419f4adbe9c56bb179
Author: Sammie Quon <sammiequon@google.com>
Date: Thu Mar 01 03:52:17 2018

webui: Move c/b/r/chromeos/quick_unlock/pin_keyboard to cr_components.

Test: trybots, manual with --show-webui-lock --show-non-md-login
Bug:  809828 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ic84f094cb9820f79df4703024b951460b1cde46b
Reviewed-on: https://chromium-review.googlesource.com/905986
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540029}
[modify] https://crrev.com/30f895bc5ffa144a1feb16419f4adbe9c56bb179/chrome/browser/resources/chromeos/quick_unlock/compiled_resources2.gyp
[delete] https://crrev.com/42772294b01a09fad925bbe120814f9703cd92fc/chrome/browser/resources/settings/people_page/pin_keyboard.html
[delete] https://crrev.com/42772294b01a09fad925bbe120814f9703cd92fc/chrome/browser/resources/settings/people_page/pin_keyboard.js
[modify] https://crrev.com/30f895bc5ffa144a1feb16419f4adbe9c56bb179/chrome/browser/resources/settings/people_page/setup_pin_dialog.html
[modify] https://crrev.com/30f895bc5ffa144a1feb16419f4adbe9c56bb179/chrome/browser/resources/settings/settings_resources.grd
[modify] https://crrev.com/30f895bc5ffa144a1feb16419f4adbe9c56bb179/ui/webui/resources/cr_components/chromeos/compiled_resources2.gyp
[add] https://crrev.com/30f895bc5ffa144a1feb16419f4adbe9c56bb179/ui/webui/resources/cr_components/chromeos/quick_unlock/compiled_resources2.gyp
[rename] https://crrev.com/30f895bc5ffa144a1feb16419f4adbe9c56bb179/ui/webui/resources/cr_components/chromeos/quick_unlock/pin_keyboard.html
[rename] https://crrev.com/30f895bc5ffa144a1feb16419f4adbe9c56bb179/ui/webui/resources/cr_components/chromeos/quick_unlock/pin_keyboard.js
[modify] https://crrev.com/30f895bc5ffa144a1feb16419f4adbe9c56bb179/ui/webui/resources/cr_components/cr_components_resources.grdp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5e1cfbc8a264f2a1167e822e858d685855b44c62

commit 5e1cfbc8a264f2a1167e822e858d685855b44c62
Author: Sammie Quon <sammiequon@google.com>
Date: Thu Mar 01 17:29:11 2018

webui: Delete md_pin_keyboard.

Remove md_pin_keyboard.html/js. It shares a lot of common code with
cr_components/chromeos/quick_unlock/pin_keyboard.html.

Modify cr_comp../c/qu/pin_keyboard to take a bunch of mixins and vars,
so the settings keyboard and lock keyboard can keep their respective
styles.

Test: manual
Bug:  809828 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I618c5325fe374c590b6e232675e77a06435d2604
Reviewed-on: https://chromium-review.googlesource.com/930480
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540198}
[modify] https://crrev.com/5e1cfbc8a264f2a1167e822e858d685855b44c62/chrome/browser/browser_resources.grd
[modify] https://crrev.com/5e1cfbc8a264f2a1167e822e858d685855b44c62/chrome/browser/resources/chromeos/login/custom_elements_lock.html
[modify] https://crrev.com/5e1cfbc8a264f2a1167e822e858d685855b44c62/chrome/browser/resources/chromeos/login/custom_elements_login.html
[modify] https://crrev.com/5e1cfbc8a264f2a1167e822e858d685855b44c62/chrome/browser/resources/chromeos/login/md_login_shared.html
[delete] https://crrev.com/3032c633775bcde85fdef8a0136a98a5320fd7e9/chrome/browser/resources/chromeos/quick_unlock/compiled_resources2.gyp
[delete] https://crrev.com/3032c633775bcde85fdef8a0136a98a5320fd7e9/chrome/browser/resources/chromeos/quick_unlock/md_pin_keyboard.html
[delete] https://crrev.com/3032c633775bcde85fdef8a0136a98a5320fd7e9/chrome/browser/resources/chromeos/quick_unlock/md_pin_keyboard.js
[modify] https://crrev.com/5e1cfbc8a264f2a1167e822e858d685855b44c62/chrome/browser/resources/settings/people_page/setup_pin_dialog.html
[modify] https://crrev.com/5e1cfbc8a264f2a1167e822e858d685855b44c62/chrome/browser/ui/webui/chromeos/login/oobe_ui.cc
[modify] https://crrev.com/5e1cfbc8a264f2a1167e822e858d685855b44c62/third_party/closure_compiler/compiled_resources2.gyp
[modify] https://crrev.com/5e1cfbc8a264f2a1167e822e858d685855b44c62/ui/login/account_picker/md_user_pod_template.css
[modify] https://crrev.com/5e1cfbc8a264f2a1167e822e858d685855b44c62/ui/webui/resources/cr_components/chromeos/quick_unlock/pin_keyboard.html
[modify] https://crrev.com/5e1cfbc8a264f2a1167e822e858d685855b44c62/ui/webui/resources/cr_components/cr_components_resources.grdp