GitLab

This adds plumbing to WebID federation requests to generate dialogs
for user permission and IDP sign-in. The prototype dialog
implementations will be added later.

Bug: 1141125
Change-Id: I37d26d8d376482c3e285907bd3eb0f56b450613b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2569379
Commit-Queue: Ken Buchanan <kenrb@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Majid Valipour <majidvp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833999}