Summary:
There is a bug currently where we don't traverse the entire tree to detect view hierarchy changes.
Currently, if you had a hierachy like this:
```
container = UIView
container.subviews = @[subview1, subview2];
subview1.subviews = @[sub11, sub12, sub13];
subview2.subviews = @[sub21, sub22, sub23];
```
and then modified via:
```
subview2.subviews = @[newView1, newView2, newView3];
```
our algorithm wouldn't identify that we had new views that needed their layout calculated, and would cause a crash later on.
Reviewed By: emilsjolander
Differential Revision: D4357662
fbshipit-source-id: 2f61f213c5f1a62948a653f3b1fa3d874c5075f7
7ec3607446