@julieqiu , There have been few changes in css code since this issue was opened.The stylesheet was modified for issue #43840. Now both the .JumpDialog and .ShortcutsDialog stays on viewport. They don't get scrolled away when the screen is scrolled.
So now my question is - is it still necessary to close the input boxes when back button is pressed? because user can now see the boxes even after pressing back button and will know they need to close input box in order to interact with rest of the page.