Search combobox is not scroll properly

Issue

If you expand combobox next to the search textbox and scroll page then position of the combobox is changing too.

Summary

Maybe it isn't most important for working page properly, but during scrolling page up you can't have combobox expanded (it will cover up some part of page). It will be fixed to screen position not to page content.

Screenshots

Before scroll

After scroll page down

I am using Google Chrome v62.0.3209.94 (64-bit) on Windows 10.