Return focus to the page after a timeout and/or mouseover

[efermi]

I often find myself switching to a tab with a mouse, reading it for a while, and after pressing Space to page down scrolling the sidebar view instead. Is it possible to return the focus to the page after a timeout and mouseover+timeout? If it is would it possible to do this within the extension (as an option) or would it need to be userChrome.js code?