GitLab

When the user disables the unified consent toggle in settings,
a metric is recorded.
This metric is added to UnifiedConsent.RevokeReason.

Bug: 868892
Change-Id: Iff196b3428b130ea4b3d71a50c2b861f5da48966
Reviewed-on: https://chromium-review.googlesource.com/1240278Reviewed-by: Scott Chen <scottchen@chromium.org>
Commit-Queue: Thomas Tangl <tangltom@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593585}