CrOS FilesApp: Allow share removable volumes with crostini

Bug: 878324
Change-Id: I50a96135175f6f16f0a33b0c95cc802f1108123c
Reviewed-on: https://chromium-review.googlesource.com/c/1298815
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602953}
4 files changed