When clicking on a user pod on the login screen, the next screen requires users to re-enter their username.  This isn't great.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/89bed32dfee51bcf0428012be7f09766543ac06a

commit 89bed32dfee51bcf0428012be7f09766543ac06a
Author: rsorokin <rsorokin@chromium.org>
Date: Thu Jan 19 10:56:43 2017

Active Directory: Propagate username to online reauth

BUG= 681028 
TEST=manual
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2641453002
Cr-Commit-Position: refs/heads/master@{#444704}

[modify] https://crrev.com/89bed32dfee51bcf0428012be7f09766543ac06a/chrome/browser/resources/chromeos/login/offline_ad_login.js
[modify] https://crrev.com/89bed32dfee51bcf0428012be7f09766543ac06a/chrome/browser/resources/chromeos/login/screen_gaia_signin.js
[modify] https://crrev.com/89bed32dfee51bcf0428012be7f09766543ac06a/chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc

bulk Verify of older or not-user-facing Chromad bugs