When you click and hold on the Button, and then drag outside, the Button remains highlighted.
This is a regression in version 2019.1.115.
Open this Dojo example. Click and hold the Button, and then drag to the right.
The Button remains highlighted, and the k-state-active class is not removed.
The Button should not be highlighted if the mouse cursor is not on the button on mouseup.
Workaround in this Dojo.