Remove usage of FOR_EACH_OBSERVER macro in ui/message_center

Remove usage of FOR_EACH_OBSERVER macro in ui/message_center

Observer lists now support range-based for loops.

BUG=655021
Committed: https://crrev.com/dfd9e46ec6757c9285ad9d7365651b461e5a6b19
Cr-Commit-Position: refs/heads/master@{#425749}

[Eric Willigers, 2016-10-15 14:03:26]

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

[commit-bot: I haz the power, 2016-10-15 14:03:32]

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

[Eric Willigers, 2016-10-15 14:03:49]

ericwilligers@chromium.org changed reviewers:
+ dewittj@chromium.org

[commit-bot: I haz the power, 2016-10-15 14:31:17]

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

[commit-bot: I haz the power, 2016-10-15 14:31:18]

Dry run: Try jobs failed on following builders:
  linux_chromium_chromeos_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[dewittj, 2016-10-17 16:04:58]

lgtm

[Eric Willigers, 2016-10-17 18:44:48]

The CQ bit was checked by ericwilligers@chromium.org

[commit-bot: I haz the power, 2016-10-17 18:45:57]

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, 2016-10-17 19:38:46]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-10-17 19:42:30]

Description was changed from

==========
Remove usage of FOR_EACH_OBSERVER macro in ui/message_center

Observer lists now support range-based for loops.


BUG=655021
==========

to

==========
Remove usage of FOR_EACH_OBSERVER macro in ui/message_center

Observer lists now support range-based for loops.

BUG=655021

Committed: https://crrev.com/dfd9e46ec6757c9285ad9d7365651b461e5a6b19
Cr-Commit-Position: refs/heads/master@{#425749}
==========

[commit-bot: I haz the power, 2016-10-17 19:42:31]

Patchset 1 (id:??) landed as
https://crrev.com/dfd9e46ec6757c9285ad9d7365651b461e5a6b19
Cr-Commit-Position: refs/heads/master@{#425749}