[Autofill]: Create a policy flag for AutofillProfileEnabled.

AutofillProfileEnabled was added as a preference setting in 1127344.
This CL creates a policy flag for AutofillProfileEnabled that can
overwrite the user preference.

Bug: 860526
Change-Id: I5d4848c26a53cf163fc4557d9b2da5f597bd98cf
Reviewed-on: https://chromium-review.googlesource.com/1127463
Reviewed-by: Lutz Justen <ljusten@chromium.org>
Reviewed-by: Drew Wilson <atwilson@chromium.org>
Reviewed-by: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574601}
8 files changed