When a tab is switched, the previous tab loses focus. But the close button
on the tab is not painted accordingly. If we point the mouse on the button
and remove (it loses focus), it is painted properly.
This affects the look and feel.

To reproduce:

Open two tabs (say A and B)
assume that the focus is on A.
Select tab B.
The tab label of A loses focus but the close button on that tab is not updated.
Point the mouse on the button and take it out
now the button on tab A loses focus and is painted properly.

Expected behaviour:

The close button should lose focus when the tab is switched.