Update inline_signin_ui to work in incognito mode

- Added a new reason for the signin that requests only the login process to
be executed and then takes the result from gaia and sends them through a new
message added to the inline_login.js. This code path avoids all cals that try
to perform operations on profiles
- This new mode is used by GCPW to gather the necessary login information

Bug: 887444

Change-Id: I84c62408b16c46a40360d7fc703b482d399cd76b
Reviewed-on: https://chromium-review.googlesource.com/c/1286755
Commit-Queue: Tien Mai <tienmai@chromium.org>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Reviewed-by: Greg Thompson <grt@chromium.org>
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Reviewed-by: Tommy Martino <tmartino@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Roger Tawa <rogerta@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607573}
39 files changed