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There should be 3 states for voice interaction
preferences: undefined, enabled, disabled. It
starts at undefined and will do a one-time-only
fetch from Android to incorporate OOBE settings.
Then the switches are managed by Chrome completely.

BUG=b:38175284

Review-Url: https://codereview.chromium.org/2968073002
Cr-Commit-Position: refs/heads/master@{#487633}