GitLab

Add an install warning for the case when an extension requests optional
host permissions that are already covered by required host permissions.

This is a follow-up to 1265118.

Bug: 859959

Change-Id: Idf639b89016ac72a4df5406d290baa177e83a0e4
Reviewed-on: https://chromium-review.googlesource.com/c/1274054
Commit-Queue: Kelvin Jiang <kelvinjiang@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600530}