[cros, user_manager] Move default user images constants and helper functions out of src/chrome.

[cros, user_manager] Move default user images constants and helper functions out of src/chrome.

BUG=387614
TBR=bauerb@chromium.org, tony@chromium.org, oshima@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=284490

[Nikita (slow), 2014-07-21 16:51:33]

This is a third part of https://codereview.chromium.org/400973002/ which already
got all lgtms so TBR'ing.

TBR'ing OWNERS of these new dependencies that were added to user_manager/DEPS

tony@:
+ui/base/l10n
+ui/base/resource

[Nikita (slow), 2014-07-21 17:06:30]

The CQ bit was checked by nkostylev@chromium.org

[commit-bot: I haz the power, 2014-07-21 17:08:15]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/nkostylev@chromium.org/402133003/40001

[tony, 2014-07-21 17:23:04]

DEPS LGTM

[commit-bot: I haz the power, 2014-07-21 19:14:35]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  ios_rel_device on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/ios_rel_device/builds...)

[commit-bot: I haz the power, 2014-07-21 19:58:00]

Change committed as 284490