Optimize display object invalidation.
Implement basic QuadTree class.
Create quad tree at stage setup.
Invalidate recursively.
Remove usage of markAsDirty.
Work with rectangle objects.
Keep quad tree reference in DisplayObject.
Update quad tree reference.
Invalidate in DisplayObjectContainer::setChildIndex/swapChildrenAt.
Fix QuadTree.
Invalidate associated display objects when drawing via Graphics API.
Get area properties from quad tree items.
Set graphics parent for programmatically created shapes.
Fix clearing of bounding caches.
Remove PreVisitor.
Start actually using the quad tree.
Use stage as target coordinate space.
Invalidate timeline objects before moving.
Set index on container children.
Clear bounding cache when updating a button.