GitLab

This makes it so icons there were downloaded more than 30 days ago
are removed. This is done to prevent the database from indefinitely
growing.

BUG=1076463
TEST=covered by tests

Change-Id: I9df9407124dd9364517bd31949ecf718fd7a9bc8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2356050
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798345}