[Accessibility, Windows8] TreeView, Narrator does not read "expanded"/"collapsed" when pressing right/left arrow

JFX build: 8u40 b10
Steps to reproduce:
1. Start Narrator on Windows 8.1.
2. Run HelloSimpleTreeView
3. Select "Root", it's already expended initially.
4. Press "Left Arrow" to collapse
Narrator reads "left arrow" instead of "collapsed". And when pressing right arrow, it reads "right arrow" instead of "expanded".

This works fine for VoiceOver on Mac.