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* When user clicks dismiss on the real Notification Setup UI in phonehub
  they can now show the UI again by clicking a button.
* When user dismisses the real onboarding UI, they can now show the UI
  again by clicking a button.

Other-
* When user dismisses the fake onboarding UI, it will be reflected to
  the toggle accurately as off.

Screenshots:
https://screenshot.googleplex.com/6eofiCBa3afSUMT
https://screenshot.googleplex.com/3YLYNsHkA6aGVKo

Bug: 1106938
Change-Id: I2fb56e1864905602a9ae769d0d9b007294fa7441
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490513Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Regan Hsu <hsuregan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820391}