[css-contain] Fix <select> dimensions with size containment

Elements with "contain: size" should be treated as having no contents,
that's not happening for <select> elements.
To fix this we add a check for size containment in
LayoutMenuList::UpdateOptionsWidth().

BUG=966673
TEST=external/wpt/css/css-contain/contain-size-select-001.html

Change-Id: Ie71a16e113d7bef4fd5c7b62e1838feba9b15cb2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1643872
Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: Manuel Rego <rego@igalia.com>
Cr-Commit-Position: refs/heads/master@{#666210}
3 files changed