ash/mus: Fix a crash during tear down.

ash/mus: Fix a crash during tear down.

WindowManagerObserver can operate on the WMShell instance when the
WindowTreeClient is destroyed (e.g. AcceleratorRegistrarImpl). So
notify the observers before destroying the WMShell instance.

BUG=639039
Committed: https://crrev.com/6d9ba42aa4635a02ddc20e9d155a055c76c510e5
Cr-Commit-Position: refs/heads/master@{#413453}

[sadrul, 2016-08-22 06:07:16]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-22 06:07:28]

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

[sadrul, 2016-08-22 06:09:10]

sadrul@chromium.org changed reviewers:
+ jamescook@chromium.org

[commit-bot: I haz the power, 2016-08-22 06:50:39]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-08-22 06:50:39]

Dry run: This issue passed the CQ dry run.

[James Cook, 2016-08-22 15:46:40]

LGTM

https://codereview.chromium.org/2269473003/diff/1/ash/mus/window_manager.cc
File ash/mus/window_manager.cc (right):

https://codereview.chromium.org/2269473003/diff/1/ash/mus/window_manager.cc#n...
ash/mus/window_manager.cc:217: FOR_EACH_OBSERVER(WindowManagerObserver,
observers_,
Can you add a comment here saying this must be destroyed before |shell_|,
something like your CL description?

(We've found such comments in ash/shell.cc to be invaluable when sorting out
init/shutdown order.)

[sadrul, 2016-08-22 15:52:20]

https://codereview.chromium.org/2269473003/diff/1/ash/mus/window_manager.cc
File ash/mus/window_manager.cc (right):

https://codereview.chromium.org/2269473003/diff/1/ash/mus/window_manager.cc#n...
ash/mus/window_manager.cc:217: FOR_EACH_OBSERVER(WindowManagerObserver,
observers_,
On 2016/08/22 15:46:40, James Cook (slow reviews) wrote:
> Can you add a comment here saying this must be destroyed before |shell_|,
> something like your CL description?
> 
> (We've found such comments in ash/shell.cc to be invaluable when sorting out
> init/shutdown order.)

Done. I looked into writing a unit-test for this, but doesn't like we have those
at the moment (we have some shell-tests in window_manager_unittest.cc, but I
don't think we can test things like this there).

[sadrul, 2016-08-22 15:52:33]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-22 15:53:09]

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

[sadrul, 2016-08-22 16:06:28]

The CQ bit was checked by sadrul@chromium.org

[sadrul, 2016-08-22 16:06:29]

The patchset sent to the CQ was uploaded after l-g-t-m from
jamescook@chromium.org
Link to the patchset: https://codereview.chromium.org/2269473003/#ps20001
(title: "doc")

[commit-bot: I haz the power, 2016-08-22 16:06:49]

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, 2016-08-22 16:29:55]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-08-22 16:31:16]

Description was changed from

==========
ash/mus: Fix a crash during tear down.

WindowManagerObserver can operate on the WMShell instance when the
WindowTreeClient is destroyed (e.g. AcceleratorRegistrarImpl). So
notify the observers before destroying the WMShell instance.

BUG=639039
==========

to

==========
ash/mus: Fix a crash during tear down.

WindowManagerObserver can operate on the WMShell instance when the
WindowTreeClient is destroyed (e.g. AcceleratorRegistrarImpl). So
notify the observers before destroying the WMShell instance.

BUG=639039

Committed: https://crrev.com/6d9ba42aa4635a02ddc20e9d155a055c76c510e5
Cr-Commit-Position: refs/heads/master@{#413453}
==========

[commit-bot: I haz the power, 2016-08-22 16:31:17]

Patchset 2 (id:??) landed as
https://crrev.com/6d9ba42aa4635a02ddc20e9d155a055c76c510e5
Cr-Commit-Position: refs/heads/master@{#413453}