Stick scrollable MPU to bottom

Start the scrollable MPU at the bottom of the page
Yeah but the offset is reading offsetHeight/width which should cause (at least in webkit browsers) reflow. I think it kind of makes sense as it needs to return the up to date values so it will reflow and recalculate with the latest data. Anyway ship it :+1:  and we can probably dig it up from the timeline in the chrome dev tools when it will be on the page.