Allow directories under Android files mount point as a download location.

In the latest Chrome OS file manager, users can copy files to directories
under the mount point for Android files.
We should allow users to specify these folders as their preferred download
location by not sanitizing such directories.

Bug: 863610
Test: unit_tests --gtest_filter=DownloadPrefsTest.DownloadDirSanitization
Change-Id: I8a9060ef743e7eb58135e3448676174f332577ac
Reviewed-on: https://chromium-review.googlesource.com/1144992
Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Naoki Fukino <fukino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578219}
2 files changed