browser_tests for sorting columns in Files

browser_tests for sorting columns in Files

This adds a test to check that clicking the columns headers in Files
resorts the columns in the correct order. It checks for ascending and
descending.

TEST=browser_tests -gtest_filter="*SortColumns/FileManagerBrowserTest*"
BUG=None

Committed: https://crrev.com/aa89c5bede6aa0b081729ef33899b13a893cb8cf
Cr-Commit-Position: refs/heads/master@{#324168}

[dhaddock1, 2015-04-07 19:40:12]

dhaddock@chromium.org changed reviewers:
+ fukino@chromium.org, mtomasz@chromium.org

[mtomasz, 2015-04-08 00:19:42]

lgtm

[mtomasz, 2015-04-08 00:19:46]

The CQ bit was checked by mtomasz@chromium.org

[commit-bot: I haz the power, 2015-04-08 00:20:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1063453003/20001

[commit-bot: I haz the power, 2015-04-08 01:21:58]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-04-08 01:23:18]

Patchset 2 (id:??) landed as
https://crrev.com/aa89c5bede6aa0b081729ef33899b13a893cb8cf
Cr-Commit-Position: refs/heads/master@{#324168}