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* Plumbs PhoneHubManager from OsSettingsManager to MultideviceSection,
  and from there NotificationAccessManager to MultideviceHandler.
* MultideviceHandler will receive NotificationAccessSetupOperation
  Status and notify the JS layer.
* MultideviceHandler listens to Cancel and Start setup events.

Bug: 1106937
Change-Id: I28a755da5f535b6b3039f1950f3458e6b3444952
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2364020
Commit-Queue: Regan Hsu <hsuregan@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800021}