Restructure responses from authenticator.mojom.

This is prep work to make way for adding the call to get an assertion
from an authenticator device.

Bug: 664630
Change-Id: I931c392b2fa523b4c05da7e6682f4c3964c5bda7
Reviewed-on: https://chromium-review.googlesource.com/830525
Commit-Queue: Kim Paulhamus <kpaulhamus@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#528136}
5 files changed