bug#50798: 28.0.50; Tab line close button is off-center until it is highlighted with the mouse

[Juri Linkov]

>> (defface test
>>   '((t :height 2.0))
>>   "")
>>
>> (defface test-tab
>>   '((default :inherit test)
>>     (t :box (:line-width 1 :style released-button)))
>>   "")
>>
>> (defface test-highlight
>>   '((default :inherit test-tab))
>>   "")
>
> Thanks, but I'm not sure I understand what you expected and why.  the
> face 'test' is defined to be twice the width of the default face.  The
> face test-highlight inherits from it, but the 't' case doesn't change
> the :height attribute, so it ends up having the same height, just with
> the :box attribute.  That's why it looks bad on the header line: its
> height is greater than that of header-line.
>
> What did you expect to happen with these definitions of faces?

My previous patch avoided inheriting from the face that changes the
height of the mouse-highlight face.  Maybe it was the right solution?