I have noticed that performance of Controls.TreeView-Keyboard benchmark has very big variation.
The difference is coming from what part of TreeView is actually scrolled.
I have modified Controls.TreeView-Keyboard to be able to scroll only through top 50
items and through last 50 items.

The performance results on Windows-XP-MidRange machine using latest build 8.0-controls-scrum-145 for TreeView of size 10,000x50 are:
 top_50: ~670 fps
 last_50: ~170 fps

JPA profile shows that in case of scrolling through last 50 items we do spend almost 10 seconds (from total 60 seconds)
in TreeUtil.getItem(TreeItem, ind, boolean). In case of scrolling through top 50 items we almost
don't spend the time there (0.002 sec).