Layout thrashing while dragging

[saravanan10393]

Expected behavior

No un-necessary layout work should happen

Actual behavior

Un-necessary layout work slows down my dragging when i have list item of 100+ items,
though I followed the optimization strategies in the given optimization help github page

Steps to reproduce

I recorded the attached video demo while using lazily loading list example

What version of React are you using?

^React 16.8.0

What version of react-beautiful-dnd are you running?

Latest

What browser are you using?

Chrome 74

Demo

https://youtu.be/q6ZHUnph53M

[alexreardon]

That looks quite laggy. The big flashes are caused by recollecting the droppable dimension for dynamic changes during a drag. We will be moving away from this strategy for #68