A bit of searching reveals that this is a limitation in Chrome that I'd encountered before but forgotten about: <option> can't be styled apart from foreground and background colors. :-(

It sounds like a common workaround is to use <ul> and <li> instead, although maybe the best approach here would be to make <settings-dropdown-menu> use <paper-menu> or <paper-listbox> instead of <select> and <option> (is there a reason why that wasn't done?). That's probably a fair bit beyond my current Polymer knowledge, though. :-)

We migrated from paper-drodpown-menu to native <select> for various reasons, see https://bugs.chromium.org/p/chromium/issues/detail?id=651513. I don't think going back is an option, there has been a lot of discussion about it. I'll cc you on related conversations.

Thanks for the context! I'll stick to the same <select>/<option> approach used by <settings-dropdown-menu>.

So, can we close this bug? There does not seem to be any action item here. FWIW, we are still considering some minor UI tweaks to the existing <select>, see https://bugs.chromium.org/p/chromium/issues/detail?id=654323 for more details.

Also the fact that you still see <paper-dropdown-menu> instances in some CrOS code, is because https://bugs.chromium.org/p/chromium/issues/detail?id=653689 has not been fully addressed yet.

Yes, it sounds like  issue 654323  (add additional horizontal padding by styling <select>) is the most that can be done as long as we're using <select>.