The tooltips are anchored to the element that caused them to be visible

in a way such that they end up adding extra space on to the bottom of

the page, which makes it so that part of the tooltip is not visible

when a comment is added to the very bottom line of the very last file

in the DiffViewer component. The user would need to scroll down to the

new bottom of the page in order to view the entirety of the tooltip.

This fix uses a flag for the tooltip positioning function that tells

the function to render the tooltip with a position that does not result

in extra space being added to the page.

I added in a comment at the very bottom line of the very last file in a

review request. The comment no longer adds space to the bottom of the

page.
I also added in another comment that was about halfway through the last

file in the review, just to make sure that comment's popup still gets

rendered the same way, since this change should not impact that case.