dillon1000/react

Deletion tracking

When we reconcile children we need to track the deletions that
happen so that we can perf side-effects later as a result. The
data structure is a linked list where the next pointer uses the
nextEffect pointer.

However, we need to store this side-effect list for reuse if we
end up reusing the progressedChild set. That's why I add a
separate first/last pointer into this list so that we can keep it
for later.