GitLab

Remove the overlay element, and instead make the menu itself a
dialog. This results in the picker being centered properly.

Bug: 855198
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: Ic77afee81667d9267a87362a80debfa2724bc05e
Reviewed-on: https://chromium-review.googlesource.com/1112063Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Commit-Queue: Kyle Milka <kmilka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569865}