Call the device/u2f sign operation and process the response.

Bug: 664630
Change-Id: Ic78e5ef9964505eb6c28a26ed771398791190fa0
Reviewed-on: https://chromium-review.googlesource.com/861644
Commit-Queue: Kim Paulhamus <kpaulhamus@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Reviewed-by: Jan Wilken Dörrie <jdoerrie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#530273}
17 files changed