Add unit tests for ArcBridgeService::RemoveObserver()

Add unit tests for ArcBridgeService::RemoveObserver()

to make sure that passing unknown pointers to the function is
harmless. https://codereview.chromium.org/2034543003/ for example
relies on the behavior.

BUG=None
TEST=try

Committed: https://crrev.com/167ddcdf336e15ce90ede703adac78d70cf3c150
Cr-Commit-Position: refs/heads/master@{#397565}

[Yusuke Sato, 2016-06-02 22:54:58]

yusukes@chromium.org changed reviewers:
+ lhchavez@chromium.org

[Yusuke Sato, 2016-06-02 22:54:59]

PTAL

[Luis Héctor Chávez, 2016-06-02 22:56:15]

lgtm thanks for doing this!

[Yusuke Sato, 2016-06-02 22:57:25]

The CQ bit was checked by yusukes@chromium.org

[commit-bot: I haz the power, 2016-06-02 22:58:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2031143002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/2031143002/1

[commit-bot: I haz the power, 2016-06-03 00:42:03]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-06-03 00:44:37]

Description was changed from

==========
Add unit tests for ArcBridgeService::RemoveObserver()

to make sure that passing unknown pointers to the function is
harmless. https://codereview.chromium.org/2034543003/ for example
relies on the behavior.

BUG=None
TEST=try
==========

to

==========
Add unit tests for ArcBridgeService::RemoveObserver()

to make sure that passing unknown pointers to the function is
harmless. https://codereview.chromium.org/2034543003/ for example
relies on the behavior.

BUG=None
TEST=try

Committed: https://crrev.com/167ddcdf336e15ce90ede703adac78d70cf3c150
Cr-Commit-Position: refs/heads/master@{#397565}
==========

[commit-bot: I haz the power, 2016-06-03 00:44:38]

Patchset 1 (id:??) landed as
https://crrev.com/167ddcdf336e15ce90ede703adac78d70cf3c150
Cr-Commit-Position: refs/heads/master@{#397565}