webauthn: add tests covering internal-UV behaviour.

Change-Id: Ic5099a0c81f028ebaef1ac83baf9a8eb7304ae7a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1504334
Commit-Queue: Adam Langley <agl@chromium.org>
Reviewed-by: Martin Kreichgauer <martinkr@google.com>
Cr-Commit-Position: refs/heads/master@{#639147}
7 files changed