Mojo C++ bindings: make StrongBinding a message loop destruction observer.

Mojo C++ bindings: make StrongBinding a message loop destruction observer.

This is a preparation for removing message loop destruction observer from mojo::Watcher.

BUG=604762
Committed: https://crrev.com/3f9ef16903199e305ae2ffb3fe74fcdd48e2ded0
Cr-Commit-Position: refs/heads/master@{#389803}

[yzshen1, 2016-04-22 22:18:39]

yzshen@chromium.org changed reviewers:
+ rockot@chromium.org

[yzshen1, 2016-04-22 22:18:40]

Hi, Ken.

Please take a look. Thanks!

[yzshen1, 2016-04-25 18:12:03]

yzshen@chromium.org changed reviewers:
+ jam@chromium.org

[yzshen1, 2016-04-25 18:12:03]

+John for the test changes in chrome/utility.

Thanks!

[Ken Rockot(use gerrit already), 2016-04-25 19:06:57]

lgtm

[jam, 2016-04-26 16:24:38]

lgtm

[yzshen1, 2016-04-26 16:30:16]

The CQ bit was checked by yzshen@chromium.org

[commit-bot: I haz the power, 2016-04-26 16:30:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1913333002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1913333002/20001

[commit-bot: I haz the power, 2016-04-26 16:35:33]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-04-26 16:37:10]

Description was changed from

==========
Mojo C++ bindings: make StrongBinding a message loop destruction observer.

This is a preparation for removing message loop destruction observer from
mojo::Watcher.

BUG=604762
==========

to

==========
Mojo C++ bindings: make StrongBinding a message loop destruction observer.

This is a preparation for removing message loop destruction observer from
mojo::Watcher.

BUG=604762

Committed: https://crrev.com/3f9ef16903199e305ae2ffb3fe74fcdd48e2ded0
Cr-Commit-Position: refs/heads/master@{#389803}
==========

[commit-bot: I haz the power, 2016-04-26 16:37:13]

Patchset 2 (id:??) landed as
https://crrev.com/3f9ef16903199e305ae2ffb3fe74fcdd48e2ded0
Cr-Commit-Position: refs/heads/master@{#389803}

[yzshen1, 2016-05-18 23:39:06]

A revert of this CL (patchset #2 id:20001) has been created in
https://codereview.chromium.org/1993063003/ by yzshen@chromium.org.

The reason for reverting is: As discussed in the mailing thread, I am thinking
to do destruction observation at the router level instead.
.