GitLab

Change downloads to use the same approach as settings, extensions, and
print preview:
(1) Use an individual grd file instead of browser_resources.grd
(2) Create unpak folder

Bug: 715296
Change-Id: Ieff03ab94d867871d62d29e217fc189434e8b03d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1605478Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658696}