Dark Mode: update Extensions loading shell

--enable-features=WebUIDarkMode --force-dark-mode to see locally.

R=rdevlin.cronin@chromium.org
BUG=883049

Change-Id: Ie34afa4952afe33f86336f49a82edc5387bc43e0
Reviewed-on: https://chromium-review.googlesource.com/c/1378682
Commit-Queue: Dan Beam <dbeam@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619212}
1 file changed