Chrome Version: 66 

What steps will reproduce the problem?
(1) Connect an external monitor. Make sure the two monitors have different scale.
(2) Open a window on one of the monitor.
(3) Press Alt-Tab on the other monitor.
(4) Hover mouse over the window UI elements.

What is the expected result?
All UI elements work and look as expected.

What happens instead?
UI elements are scaled incorrectly.