The function tab-bar-auto-width determines which tabs to automatically
resize based on the face applied to each tab's text.  If the face is one
of tab-bar-auto-width-faces, then the tab gets resized.  However, if
either tab-bar-tab-face-function or tab-bar-tab-group-face-function is
set to a function which does not apply one of tab-bar-auto-width-faces,
then the tabs which have a different face are not auto resized.

A real-world example of this issue is in activities.el:

https://github.com/alphapapa/activities.el/issues/76

In the proposed patch, instead of checking each tab's face, we check
that the symbol at the start of each tab keymap matches

(rx bos (or "current-tab" "tab-" "group-"))

Thank you!!

Joseph