Add policy for handling unsupported filetypes regarding DLP and Malware scans.

Change-Id: I020f5d635ec4ea3b12410652cb64a64449565c22
Bug: 1013584
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2020893
Commit-Queue: Steph Lee <stephlee@google.com>
Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Reviewed-by: Daniel Rubery <drubery@chromium.org>
Reviewed-by: Roger Tawa <rogerta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736547}
6 files changed