'scroll-bar-height' to set horizontal scroll bars and their height
for individual frames and in 'default-frame-alist'.
+***** The 'horizontal-scroll-bars' parameter was already present and non-nil
+by default in Emacs 24 (although it didn't have any effect). This
+could cause a problem if you share your desktop files with Emacs 24:
+saving desktop in v24, then restoring it in v25.1 would turn on
+horizontal scroll bars in all buffers. To resolve this issue, put
+this in your ~/.emacs init file
+
+ (modify-all-frames-parameters '((horizontal-scroll-bars . nil)))
+
**** New functions 'frame-scroll-bar-height' and
'window-scroll-bar-height' return the height of horizontal scroll
bars on a specific frame or window.