Migrate existing WebAuthN components to WD07.

Correctly return TypeErrors instead of DomExceptions for 
missing Rp & User Entity elements.

Bug: 664630
Change-Id: I464a3d2555f2599299238768a8ef59e8b32cb7f6
Reviewed-on: https://chromium-review.googlesource.com/741863
Commit-Queue: Kim Paulhamus <kpaulhamus@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519871}
45 files changed