Fix flaky Kiosk browser_tests failing on wrong widget opacity.

Fix flaky Kiosk browser_tests failing on wrong widget opacity.

Ash was trying to show the shelf with its widget opacity set to 0.0 causing
a DCHECK crash in the tests. This makes sure the opacity of the system tray's
widget is set properly when it's shown or hidden.

Also re-enables a test that was disabled previously since it's passing now due
to this CL.

BUG=624584
TEST=browser_tests --gtest_filter=KioskEnterpriseTest.PrivateStore
TEST=browser_tests --gtest_filter=KioskUpdateTest.IncompliantPlatformFirstInstall

Committed: https://crrev.com/1828054aceaf6bc19e5ac5c5bc49689c47930df3
Cr-Commit-Position: refs/heads/master@{#403489}

[afakhry, 2016-07-01 17:55:16]

afakhry@chromium.org changed reviewers:
+ xiyuan@chromium.org

[afakhry, 2016-07-01 17:55:17]

Xiyuan, please review. Thank you!

[xiyuan, 2016-07-01 18:04:48]

lgtm

[afakhry, 2016-07-01 18:05:56]

The CQ bit was checked by afakhry@chromium.org

[commit-bot: I haz the power, 2016-07-01 18:06:11]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-07-01 18:34:23]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-07-01 18:36:59]

Description was changed from

==========
Fix flaky Kiosk browser_tests failing on wrong widget opacity.

Ash was trying to show the shelf with its widget opacity set to 0.0 causing
a DCHECK crash in the tests. This makes sure the opacity of the system tray's
widget is set properly when it's shown or hidden.

Also re-enables a test that was disabled previously since it's passing now due
to this CL.

BUG=624584
TEST=browser_tests --gtest_filter=KioskEnterpriseTest.PrivateStore
TEST=browser_tests
--gtest_filter=KioskUpdateTest.IncompliantPlatformFirstInstall
==========

to

==========
Fix flaky Kiosk browser_tests failing on wrong widget opacity.

Ash was trying to show the shelf with its widget opacity set to 0.0 causing
a DCHECK crash in the tests. This makes sure the opacity of the system tray's
widget is set properly when it's shown or hidden.

Also re-enables a test that was disabled previously since it's passing now due
to this CL.

BUG=624584
TEST=browser_tests --gtest_filter=KioskEnterpriseTest.PrivateStore
TEST=browser_tests
--gtest_filter=KioskUpdateTest.IncompliantPlatformFirstInstall

Committed: https://crrev.com/1828054aceaf6bc19e5ac5c5bc49689c47930df3
Cr-Commit-Position: refs/heads/master@{#403489}
==========

[commit-bot: I haz the power, 2016-07-01 18:37:00]

Patchset 1 (id:??) landed as
https://crrev.com/1828054aceaf6bc19e5ac5c5bc49689c47930df3
Cr-Commit-Position: refs/heads/master@{#403489}