Bug 1637010 - Fix how the scroll position is computed for position:sticky line clicks
Bug 1637010 - Fix how the scroll position is computed for position:sticky line clicks

The nesting container is rooted at the stuck line's original offset, so
scrolling up by the difference between the two correctly jumps to the line
number that was clicked.

bill-mccloskey/searchfox,bill-mccloskey/searchfox,bill-mccloskey/searchfox,bill-mccloskey/searchfox,bill-mccloskey/searchfox,bill-mccloskey/searchfox