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* Update chrome://settings Privacy section to change int kNetworkPredictionOptions
instead of bool kNetworkPredictionEnabled.
* Introduce code to migrate user setting (and only user setting).
* Per UI review, keep UI unchanged.
* Note that policy handler for these two preferences has already landed, see https://crrev.com/431493003.

BUG=334602

Review URL: https://codereview.chromium.org/421653006

Cr-Commit-Position: refs/heads/master@{#288352}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288352 0039d316-1c4b-4281-b951-d872f2087c98