bug#73862: [PATCH] Add `header-line-active` and `header-line-inactive` faces.

[Eli Zaretskii]

> From: Eshel Yaron <me@eshelyaron.com>
> Cc: trevor.m.murphy@gmail.com,  monnier@iro.umontreal.ca,
>   aaronjensen@gmail.com,  73862@debbugs.gnu.org
> Date: Sun, 08 Dec 2024 21:56:33 +0100
> 
> Aaron shared a recipe to reproduce this behavior, copied here:
> 
> --8<---------------cut here---------------start------------->8---
> (setq header-line-format "Some header")
> (face-remap-set-base 'header-line 'highlight)
> (switch-to-buffer-other-window "new")
> ;; In new buffer/window:
> (setq header-line-format "Some header")
> (other-window 1)
> ;; In original buffer/window:
> (set-face-attribute 'default nil :height (+ (face-attribute 'default :height) 
> 10))
> --8<---------------cut here---------------end--------------->8---

Are you also change the attributes of the default face to cause the
"spreading"?  If not, please show a recipe.  Because I was unable to
see this without something like the last line of the recipe, and also
that line _must_ be in the buffer where header-line is remapped,
otherwise the effect is not seen.