Fixes crash in ~ShellConnection

Fixes crash in ~ShellConnection

Code was assuming a WindowManagerConnection has been created, which is
not necessarily the case. In particular if you run a single test and
the test doesn't talk to mus you hit the check.

BUG=613018
TEST=test only change
R=sadrul@chromium.org

Committed: https://crrev.com/56172f6d40ecf4dc259a05d37df4bd2ac8789846
Cr-Commit-Position: refs/heads/master@{#394795}

[sadrul, 2016-05-19 16:21:55]

lgtm

[sky, 2016-05-19 16:28:49]

The CQ bit was checked by sky@chromium.org

[commit-bot: I haz the power, 2016-05-19 16:29:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1998543004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1998543004/1

[commit-bot: I haz the power, 2016-05-19 16:43:08]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-05-19 16:45:58]

Description was changed from

==========
Fixes crash in ~ShellConnection

Code was assuming a WindowManagerConnection has been created, which is
not necessarily the case. In particular if you run a single test and
the test doesn't talk to mus you hit the check.

BUG=613018
TEST=test only change
R=sadrul@chromium.org
==========

to

==========
Fixes crash in ~ShellConnection

Code was assuming a WindowManagerConnection has been created, which is
not necessarily the case. In particular if you run a single test and
the test doesn't talk to mus you hit the check.

BUG=613018
TEST=test only change
R=sadrul@chromium.org

Committed: https://crrev.com/56172f6d40ecf4dc259a05d37df4bd2ac8789846
Cr-Commit-Position: refs/heads/master@{#394795}
==========

[commit-bot: I haz the power, 2016-05-19 16:45:59]

Patchset 1 (id:??) landed as
https://crrev.com/56172f6d40ecf4dc259a05d37df4bd2ac8789846
Cr-Commit-Position: refs/heads/master@{#394795}