The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/563db89fe789e2147cdc0a7b2a52079e80970307

commit 563db89fe789e2147cdc0a7b2a52079e80970307
Author: rsorokin <rsorokin@chromium.org>
Date: Wed Dec 21 15:53:29 2016

Enable Active Directory shortcut on the welcome screen

BUG= 668459 
TEST=manual

Review-Url: https://codereview.chromium.org/2577093002
Cr-Commit-Position: refs/heads/master@{#440110}

[modify] https://crrev.com/563db89fe789e2147cdc0a7b2a52079e80970307/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
[modify] https://crrev.com/563db89fe789e2147cdc0a7b2a52079e80970307/ui/login/display_manager.js

@rsorokin, is the Ctrl-Shift-Alt-A shortcut still required/still valid.
IIRC, this shortcut has been removed in later versions of ChromeOS ie, M60+. 

Yes, it was removed. Should not work at all now.