Make test names in the sheriff-o-matic examine page selectable

Don't use paper item. That makes things unselectable, but it also adds
the ink effect, which is weird once the text is selectable. Instead,
just use a regular old div. <core-menu> still does all the real work
of selecting items.

BUG=404043
NOTRY=true

Review URL: https://codereview.chromium.org/498653002

git-svn-id: svn://svn.chromium.org/blink/trunk@180803 bbb929c8-8fbe-4397-9dbb-9b2b20218538