The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/eb3d8e91dd4c6f664d7c54f616ccb2ca4a6f9620

commit eb3d8e91dd4c6f664d7c54f616ccb2ca4a6f9620
Author: Naoki Fukino <fukino@chromium.org>
Date: Fri May 18 04:06:10 2018

Show migration UI on Linux when the test flag is enabled.

When the flag for testing the migration UI (--test-encryption-migration-ui)
is enabled, we should show the migration UI regardless of the policy check.
In addition, I added the check for force_dircrypto_if_available() in
FakeCryptohomeClient to make SKIP button working.

Bug:  844023 
Test: On Linux, build and run Chrome for ChromeOS with --test-encryption-migration-ui --login-manager --show-webui-login (needed to work around  issue 844020 ) and check that I can see migration screen and SKIP button works.
Change-Id: I56664a3976e10bd6bad27dcfcb1ce2503a117fc5
Reviewed-on: https://chromium-review.googlesource.com/1064032
Commit-Queue: Naoki Fukino <fukino@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559795}
[modify] https://crrev.com/eb3d8e91dd4c6f664d7c54f616ccb2ca4a6f9620/chrome/browser/chromeos/login/existing_user_controller.cc
[modify] https://crrev.com/eb3d8e91dd4c6f664d7c54f616ccb2ca4a6f9620/chromeos/dbus/fake_cryptohome_client.cc