Add a wpt for UAv2 frame hierarchy check.

The test passes manually.

Bug: 978620
Change-Id: Ic40cef889d41c8b21e8e184d158ecdd2b92ebabd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1677067
Reviewed-by: Navid Zolghadr <nzolghadr@chromium.org>
Commit-Queue: Mustaq Ahmed <mustaq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672503}
4 files changed