Bug: strange pixel gaps on bottom with `visible` targetModifier

[kizu]

Here is an example: http://codepen.io/kizu/pen/wDyzE and the full-page view: http://codepen.io/kizu/full/wDyzE/

I can see there two problems:

1. On the editor view on CodePen you can see that there is one extra pixel on the bottom, while on the full page the block is positioned properly. This is strange.
2. Moreover: on both views when you scroll all the way to the bottom there is a two pixel gap at the bottom.

What is expected: when the element is attached to the bottom of the block's visible area, it should always be at the bottom of it, without any gaps. Maybe there are some rounding errors that prevent it from happening?

[RobbieTheWagner]

@kizu I realize this is a super old issue, but I just took a look at the CodePen and I do not see any issues. Are you still seeing it?

[RobbieTheWagner]

Just kidding, I do see the issue still. I think something about _getActualBoundingClientRect is getting a value that is a couple pixels off.