Summary:
This colours data model nodes in the tree to show how they were part of the current changeset: whether the data model caused an insert, update, remove etc.
This also adds phantom Section nodes for Sections that were completely removed from the tree; this is helpful for debugging cases where a section's key changes without intention, causing items to be completely removed and inserted.
Reviewed By: topwu
Differential Revision: D16165767
fbshipit-source-id: a011666dce33e4d757fb415e71ba163aa334f6e6
474cc1289e