Reset avatar image when the avatar policy becomes unset

Reset avatar image when the avatar policy becomes unset

When the avatar policy is cleared, the user can pick an avatar image
again. Until the user does this, Chrome has two options:
1) keep using the image that had most recently been set through policy
2) revert to a default image

Chrome's current behavior is (1). This CL changes it to (2), which may be
easier to understand for users and is consistent with the behavior of the
wallpaper policy.

BUG=380422
TEST=Updated browser test

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=275289

[bartfab (slow), 2014-06-05 14:05:55]

Hi Pavel,

Could you take a look at this CL please?

[dzhioev (left Google), 2014-06-05 17:01:15]

LGTM

[bartfab (slow), 2014-06-05 17:05:23]

The CQ bit was checked by bartfab@chromium.org

[commit-bot: I haz the power, 2014-06-05 17:06:18]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/bartfab@chromium.org/315213002/1

[commit-bot: I haz the power, 2014-06-05 20:05:01]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_chromium_x64_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/win_chromium_x64_rel/...)

[commit-bot: I haz the power, 2014-06-06 01:15:08]

Change committed as 275289