Override user data directory to the temp for ProfileInfoCacheTest.

Override user data directory to the temp for ProfileInfoCacheTest.

Currently the tests of this suite (or, at least,
DownloadHighResAvatarTest) read and write to the default system-wide
location, which is not good and can cause tests flakiness.

Now we override the DIR_USER_DATA to a temporary directory instead.

BUG=486785
Committed: https://crrev.com/a2e114926ad900ec3c34a623fdae85832f163624
Cr-Commit-Position: refs/heads/master@{#329429}

[emaxx, 2015-05-11 19:00:07]

emaxx@chromium.org changed reviewers:
+ mlerman@chromium.org

[emaxx, 2015-05-11 19:00:08]

Hi Michael, please take a look at this CL with tests fix.

[Mike Lerman, 2015-05-12 17:05:34]

lgtm

[emaxx, 2015-05-12 17:12:51]

The CQ bit was checked by emaxx@chromium.org

[commit-bot: I haz the power, 2015-05-12 17:13:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1138003004/1

[commit-bot: I haz the power, 2015-05-12 17:19:17]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-12 17:21:09]

Patchset 1 (id:??) landed as
https://crrev.com/a2e114926ad900ec3c34a623fdae85832f163624
Cr-Commit-Position: refs/heads/master@{#329429}