1) go to google, search for "hest" or something else.
2) Then mouse over the >> signs for an element.
3) Now scroll to the top, then down (enough to make the overlay fixed) then down quickly...
Result: the google logo looks non-smooth, then after 0.5 sec looks fine.
Closing this bug because the EFL port has been removed from trunk.
If you feel this bug applies to a different upstream WebKit port and was closed in error, please either update the title and reopen the bug, or leave a comment to request this.