WebAuthentication: Add chrome://flags#enable-webauthentication.

This patch adds a flag to enable support for PublicKeyCredentials in
CredentialManager.

Bug: 664630
Change-Id: Icbdfc6318dd1d3bce65136e826f2bb1f4da1c04e
Reviewed-on: https://chromium-review.googlesource.com/873390
Commit-Queue: Kim Paulhamus <kpaulhamus@chromium.org>
Reviewed-by: Kim Paulhamus <kpaulhamus@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#530287}
4 files changed