GitLab

Adds a function to |MenuDelegate| that can be overloaded to create a
footnote View for a top-level menu.

The footnote view is rendered at the bottom of the menu, with a
different background color, similar to
|BubbleFrameView::SetFootnoteView()|.

Bug: 889229, 894193
Change-Id: Icb67740fddfe03a7a2d9bae7c70b383cfe6a9845
Reviewed-on: https://chromium-review.googlesource.com/c/1277573Reviewed-by: Michael Wasserman <msw@chromium.org>
Commit-Queue: Nicolas Ouellet-Payeur <nicolaso@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599881}