Move UserContext to its own file

Move UserContext to its own file

This CL moves the UserContext from user.[cc|h] to its own header and
implementation files.

BUG=367847
TEST=Updated unit and browser tests

TBR=nkostylev (chrome/browser/chromeos/app_mode/kiosk_profile_loader.cc)
TBR=nkostylev (chrome/browser/chromeos/chrome_browser_main_chromeos.cc)
TBR=pamg (chrome/browser/managed_mode/chromeos/manager_password_service.[cc|h])

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=271424

[bartfab (slow), 2014-05-15 13:57:26]

Hi Denis,

Could you take a look please?

[Denis Kuznetsov (DE-MUC), 2014-05-15 14:19:19]

lgtm

[bartfab (slow), 2014-05-19 13:11:00]

The CQ bit was checked by bartfab@chromium.org

[commit-bot: I haz the power, 2014-05-19 13:11:32]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/bartfab@chromium.org/290513003/10001

[commit-bot: I haz the power, 2014-05-19 15:00:32]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  android_dbg_triggered_tests on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_dbg_triggered...)

[commit-bot: I haz the power, 2014-05-19 15:51:53]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-05-19 15:51:53]

Try jobs failed on following builders:
  android_dbg_triggered_tests on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_dbg_triggered...)

[bartfab (slow), 2014-05-19 16:34:19]

The CQ bit was checked by bartfab@chromium.org

[commit-bot: I haz the power, 2014-05-19 16:34:28]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/bartfab@chromium.org/290513003/10001

[commit-bot: I haz the power, 2014-05-19 18:09:13]

Change committed as 271424