I have to admit, this method confuses me.  I'm not sure its clear what it's doing based on its name.  If I'm interpreting the code correctly, this method is used to tell the delegate that the content size of the collection view has changed, and we've updated the sizing constraints on that collection view accordingly.  The callee can use that opportunity to ignore, animate, instantly pop the change onscreen, etc.

I'm having a hard time thinking of a good name based on that interpretation though.  Maybe ```contactPicker:didUpdateContactCollectionViewHeightTo:```?