Directory for reputation warnings.

This CL adds a directory for upcoming reputation warnings
and the safety tip experiment. Otherwise, this CL
contains nothing interesting.

Bug: 981177
Change-Id: Ic5a4bfc7ce5f95ccdf04e8a9604aa6fe094b2411
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1688332Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Mustafa Emre Acer <meacer@chromium.org>
Commit-Queue: Joe DeBlasio <jdeblasio@chromium.org>
Auto-Submit: Joe DeBlasio <jdeblasio@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685386}

chrome/browser/reputation/OWNERS

+jdeblasio@chromium.org
+estark@chromium.org
+meacer@chromium.org

chrome/browser/reputation/README

+This directory stores files related to Chrome's reputation warnings.
+
+If Chrome believes a site a user is visiting is low reputation, either due to
+failing heuristics or models in Chrome, or as determined server-side, Chrome may
+warn users about this state. This warning may either be a full-page interstitial
+warning or a pop-up while visiting the page.
+
+This warning will not trigger on sites that are not likely to be actively
+malicious, such as popular sites or sites with high engagement scores.