Show error when all files being transferred are inaccessible

When transferring files, if only some of files being transferred
inaccessible, the progress center will display an error. However, when
all the files being transferred are inaccessible, no error will appear
as nothing was transferred. Change it so that errors also appear when no
files are successfully transferred.

Bug: 910500
Change-Id: I0317949f6bf2d0eff4f39cab6c7fe5e94b37a486
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1580992
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Austin Tankiang <austinct@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654337}
3 files changed