Revert "Simplify PriorityNestedScrollConnection"

This reverts commit 40c5c2310e87c5b998d0263967cc89e230be7074.

Reason for revert: Causes weird gesture issues; single swipes could now
trigger multiple vertical + horizontal transitions.

Change-Id: I16f37ace7b436fb2502f476ea83c1421933d5860
7 files changed