rAF in Scrollable Area

[snewcomer]

Looking at using this addon in Safari, if in a scrollable container, getBoundingClientRect is computed based off of the window. So if the table is set 200px below or at the top of the screen, getBoundingClientRect on the element (sentinel) may not be sufficient.

If using scrollable container, we need to also get the client rect for the scrollable container and determine if in viewport IFF bottom (sentinel) - bottomTolerance (scrollable) <= height (scrollable) + top (scrollable).