Comment 6 for bug 155483

It's the emacs-extra package:

$ grep -C 3 bar-mode /usr/share/emacs/site-lisp/emacs-extra/emacs-extra.el
(defun down-a-lot () (interactive) (scroll-down))
(global-set-key [C-mouse-4] 'down-a-lot)
(global-set-key [C-mouse-5] 'up-a-lot)
(menu-bar-mode nil)
(set-scroll-bar-mode nil)
(when (>= emacs-major-version 21)
  (tool-bar-mode -1)
  (blink-cursor-mode nil)
  (require 'zone)
  (setq zone-idle 300)

This toggles the menu bar and the scroll bar, and turns off the tool bar when emacs-major-version is greater than 21.

It also turns on zone, which was another nasty surprise after the upgrade (when zone kicks in, my laptop heats up to about 7000C).

Attached is a proposed patch.