Given a button with the focus, resize the window. As the window
is resized, it appears that the focus highlight is being redrawn
continually.

Normal focus highlight is shown in attachment normal.png.

Resizing the window larger will cause the highlight to grow larger.
If you resize really quickly to the edge of the screen, the focus
highlight will turn into a large blob and may get stuck. See attachment
expanded.png for example.

If you resize the window smaller, the focus highlight will also get smaller
and will disappear behind the button. See shrunk.png for example.

I'm splitting this bug from RT-8169, leaving that bug to cover Swing pipeline
issues.

The focus highlight is drawn by the Region code, I think.