This problem can be reproduced on any site with a <select>, here's one:
https://output.jsbin.com/mogiwev

In Chrome 59, select options became taller on touchscreens on windows. However, this also happens when using an external display. I helped the maintainer of https://bulbs.se/ bisect this problem, where it initially looked like options had just gotten taller for no particular reason. Results were:

You are probably looking for a change made after 463188 (known good), but no later than 463195 (first known bad).
CHANGELOG URL:
  https://chromium.googlesource.com/chromium/src/+log/0bd89391dc79ae15c314d632f5829b0d430cf9af..5136241948671b538965c783e8aee27e88037aa9

And the culprit is https://chromium.googlesource.com/chromium/src/+/112094796a99ff35f551467912814d08935b6055

Arguably, when only using an external display that isn't a touch screen, then this should not happen.