GitLab

Make MenuItemView's delegate an optional argument in its constructor so
it can be default constructed. Its delegate can always be set thru the
existing set_delegate() function. Also need to add a few more checks for
the return delegate pointer.

Bug: 1108460
Change-Id: Ie90709271c971cadccf3e13166df0c240d73dfca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2321526Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Wei Li <weili@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792836}