Add enterprise policy for safe browsing extended reporting

The policy disables opt-in to extended reporting (checkbox does not show
up, and reports are not sent).

BUG=461593

Review URL: https://codereview.chromium.org/1056613003

Cr-Commit-Position: refs/heads/master@{#324499}
14 files changed