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Preivously, notifier settings was accessible from Notification Center.
In UnifiedSystemTray, System Tray and Notification Center are merged,
and notifier settings is accessible as a detailed view of Do not disturb
feature pod item.

Screenshot: http://screen/f2PaXeD71LQ

TEST=manual
BUG=835733

Change-Id: Ia6302647ebb837c4f8b494a150509273f0d56161
Reviewed-on: https://chromium-review.googlesource.com/1100719Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
Commit-Queue: Tetsui Ohkubo <tetsui@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567562}