Summary:
More fine grained dirty marking
Currently a node's dirty flag propagates to the root of the tree ensuring that when any node is invalidated its whole subtree will be re-calculated. This is often times not needed. There are many properties which only effects a node's children and would not need to propagate all the way to the root such as align-items. Also in cases where the style does change layout it may not need to propagate all the way to the root but can often stop at the nearest position: absolute parent.
This change has the potential of greatly improving performance of re-calculating a tree.
This might require adding a second dirty flag named hasDirtyDescendants ensuring that traversal still works even though a parent is not marked as dirty.
Reviewed By: emilsjolander
Differential Revision: D6134754
fbshipit-source-id: bbcfee14058140b946401de756a3f130de0f51cd
c5182c4bf5