Use the new Result type in file-transfer code.

Bug: 679313
Change-Id: Iedb6d88e54849fd7f68d59f4261be9b78228a837
Reviewed-on: https://chromium-review.googlesource.com/c/1401280
Reviewed-by: Martin Barbella <mbarbella@chromium.org>
Reviewed-by: Joe Downing <joedow@chromium.org>
Reviewed-by: Lambros Lambrou <lambroslambrou@chromium.org>
Commit-Queue: Erik Jensen <rkjnsn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623821}
21 files changed