JDK9 b136, OS X 10.11, Retina (not sure if it does matter)

the issue is easy reproducible with built-in touchpad, wasn't able to reproduce with the mouse on the same machine.

Please run the attached test code and click to see the drop-down tab list. sometimes it is not rendered properly (see "tabs-nok-1.mov", 00:12 and 00:23)

at a 1st glance, not reproducible with JDK8