Version: 53.0.2785.46
OS: Windows 10

What steps will reproduce the problem?
(1) Enable chrome://flags/#overlay-scrollbars
(2) Open any page with scrolling (e.g. bokan.ca/iframe.html)
(3) Use touchscreen to shrink the window

What is the expected output?
The overlay scrollbars shouldn't expand

What do you see instead?
The overlay scrollbars expand and don't shrink back until the user taps somewhere else or moves the mouse within the window. It also seems that the behavior is different when making the window bigger, the scrollbars don't expand in that case. I suspect this is related to  issue 332227  and is more generally described as "mouse events synthesized from touch cause unexpected activation of overlay scrollbars".