This change adds the Mojo implementation of authenticator.mojom's MakeCredential.

The remainder of the implementation to call U2F.register() is in a follow-up CL.

BUG=664630
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/2788823002
Cr-Commit-Position: refs/heads/master@{#483675}
24 files changed