Fix BasicListMenu#getMenuDimensions to account for submenus

Otherwise, the width and height of the header are not used, so the popup window may be too narrow or too short.

Pair-programmer: mschillaci

Before: https://screencast.googleplex.com/cast/NTAzNjM2MDA5NTIzNjA5Nnw4MTExZTg0OC04YQ

After: https://screencast.googleplex.com/cast/NTE3NDcyNDQxMjgzMzc5Mnw3OGE0ZjFjNC0xZQ

Fixed: 444053452
Change-Id: Ibb83707d86e1cadf0dbbbf071d016afe85a7edba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6936718
Reviewed-by: Xi Han <hanxi@chromium.org>
Reviewed-by: Wenyu Fu <wenyufu@chromium.org>
Commit-Queue: Jenna Himawan <jhimawan@google.com>
Cr-Commit-Position: refs/heads/main@{#1514630}