REG[5.4 - 5.5] QtWebEngine scrollbars with hidpi hangs webpage loading

Go to Windows control panel->appearance and Personalization -> Display
and set "Change the size of all items" to 150% or 200%.

Run Webengine browser example in hidpi screen and try to open page that cause scrollbar to the windows (http://qt.io). Result is that webpage hangs and won't open.

It's also reported that with 4K display default scrollbars are painted red and won't follow the css style.