graduation: Add screen containing Takeout <webview>

+ Added Takeout webview preceded by a loading screen.

Demo: http://screencast/cast/NTAwNjk0MTExNjk1NjY3MnwzYzMyMjhiZi1iMg
Bug: b:357877669, b:360137115
Change-Id: I083536cf0554a0d6e52f680294cecd33d39aed07
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5805131


Reviewed-by: Courtney Wong <courtneywong@chromium.org>
Reviewed-by: Aga Wronska <agawronska@chromium.org>
Commit-Queue: Amber Haynes <amberhaynes@chromium.org>
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1349423}