GitLab

- Renames download_directory_util.cc to download_directory_util.mm.
- Adds UIFileSharingEnabled flag to info.plist. It allows access to user's Documents.
- Moves downloads folder to user's Documents.
- Makes downloaded files persistent.

Bug: 1013072
Change-Id: Idf4e92455babe678c1c8551cad06638f1003ba72
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1856099
Commit-Queue: Ewann Pellé <ewannpv@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712979}