We were investigating/discussing bugid 4679721, and I observed the following
behavior when running /test/java/awt/Focus/WindowTest

Click on the thumb of the vertical scrollbar.
Instead of the thumb blinking, I see blinking at the bottom
of the scrollbar track.

Click on the bottom arrow of the vertical scroll bar.
The thumb starts blinking.

I clicked around the applet for a little while.
Then, I clicked on the thumb of the vertical scrollbar.
It started blinking.
I grabbed the scroll bar with the mouse and dragged it down.
The blinking rectangle stayed where it was on the scroll bar
track - it did not stay over the thumb, even after I stopped
dragging the thumb.

If you use tab to move focus away from the scroll bar,
sometimes the thumb stays highlighted (but does not blink).
Another component is highlighted and takes focus though.