Transitioning between lists with the keyboard does not respect container clipping

[jaredcrowe]

Bug or feature request?

Bug

Expected behaviour

When moving between lists with the keyboard, a droppable's dimension will be clipped if it's within in a scroll container.

Actual behaviour

A droppable's dimensions do not appear to be clipped by a scrollable parent.

Steps to reproduce

On the multiple vertical lists stress test story:

1. Add a lot of items to the epsilon board
2. Scroll all the way to the bottom of epsilon's container
3. Try to move an item into the delta board with the keyboard

Browser version

Chrome Version 61.0.3163.100 (Official Build) (64-bit)

Demo

https://drive.google.com/file/d/0B9It2FnzHQ-vSmFvVGZOVW5OTE0/view

[jaredcrowe]

Hoping this will be an easy fix once #132 gets in.

[alexreardon]

Was this created by the last clipping change?

[jaredcrowe]

Yeah I expect it probably would have been :( This issue only pops up when you've got long droppables inside scroll containers sitting on the same main axis - I'll add some tests to make sure we cover this case.