Implement some more updates in the WebAuthN spec WD07 updates.

 -- Remove hashAlgorithm from CollectedClientData (SHA-256 is hardcoded).
 -- Make userhandle optional in AuthenticatorAssertionResponse.
 -- Rename Attachment to AuthenticatorAttachment.

Bug: 664630
Change-Id: Id4e8d86eb581bfdd556618c17bdab877670556a2
Reviewed-on: https://chromium-review.googlesource.com/873993
Commit-Queue: Kim Paulhamus <kpaulhamus@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#530484}
6 files changed