The bug is reproducible starting from b70. It looks like the regression from fix for 4397557. I confirmed that removing that fix restores normal behavior.
Steps to reproduce:
1. Run regression test test/java/awt/Focus/WindowTest
2. Click on button "Button" by mouse to make it focused.
3. Press Tab key several times so Choice will become focused.
4. Press Space, Choice's menu will appear.
5. Using arrow keys try to select item and press Space to accept the selection and to close the menu. - Starting from b70 you will not be able to do this. There is no other way to select or close the menu other then by mouse.